Consensus-Based Guidelines for the Recognition, Diagnosis, and Management of Hemophagocytic Lymphohistiocytosis in Critically Ill Children and Adults

Chinese expert consensus on the application of intravenous immunoglobulin in hematological diseases

Intravenous immunoglobulin (IVIG), first developed for the treatment of patients with antibody deficiencies, is now widely used in clinical practice, especially in hematological and immune system diseases, and its application in hematological oncology chemotherapy, cellular immunotherapy and hematopoietic stem cell transplantation (HSCT) is becoming more and more common. The Chinese Collaborative Group for Infection Immunology and Microecology Research Translation Collaborative Group organized relevant experts to discuss and propose the "Chinese expert consensus on the application of intravenous immunoglobulin in hematological diseases," which was formulated based on the progress of research on the application of IVIG in blood diseases, and provides a basis for the standardization of the use of IVIG in hematologic disorders.

[Secondary hemophagocytic lymphohistiocytosis due to icteric leptospirosis with acute renal failure]

A 51-year-old patient presented himself with fever, upper abdominal pain and exertional dyspnea. Hemodynamic instability accompanied by generalized icterus, hepatosplenomegaly, a morbilliform rash with petechia and bilateral conjunctivitis revealed in clinical examination.Laboratory results revealed elevated C-reactive protein and procalcitonin as well as pancytopenia and hyperbilirubinemia. Furthermore hypertriglyceridemia, hyperferritinemia and elevated soluble IL-2-receptor were found. Testing for infectious diseases detected IgM-antibodies to leptospires. Bone marrow cytology featured hemophagocytosis.Secondary hemophagocytic lymphohistiocytosis due to icteric leptospirosis (Weil's disease) was diagnosed.Immediate antibiotic therapy and circulatory support by fluid and vasopressors was initiated and non-invasive ventilation and hemodialysis stabilized the patient. With steroids and polyvalent immunoglobulins the organ functions recovered.Hemophagocytic lymphohistiocytosis is an important differential or concomitant diagnosis in sepsis and can be induced by rarely diagnosed infectious triggers like leptospirosis.

Clinical Characteristics and Treatment of Familial Hemophagocytic Lymphohistiocytosis

Familial hemophagocytic lymphohistiocytosis (fHLH) comprises a group of autosomal recessive disorders characterized by germline loss-of-function variants that negatively impact lymphocyte cytotoxicity. These disorders exhibit variable clinical presentations, most often in association with severe hyperinflammation. fHLH is diagnosed through clinical and laboratory assessments as well as genetic testing and immunologic assays. In the absence of therapy to control the hyperactive immune system, fHLH is generally fatal. Treatment has historically taken the form of cytotoxic chemotherapy and/or immunosuppressive therapy, although targeted inhibitors of inflammatory cytokines and their downstream signaling are increasingly being utilized. Definitive treatment requires allogeneic hematopoietic cell transplantation.

Multidisciplinary approach to treating complex immune dysregulation disorders: an adaptive model for institutional implementation

Patients with immune dysregulation may present with varying combinations of autoimmunity, autoinflammation, immunodeficiency, atopy, lymphoproliferation, and/or malignancy, often with multisystem involvement. Recognizing specific patterns of immune dysregulation, coordinating and interpreting complex diagnostic testing, and choosing initial (often empiric) treatment can be challenging. Centers are increasingly assembling multidisciplinary teams (MDTs) to standardize evaluation and optimize treatment of patients with complex immune dysregulation (immune dysregulation MDTs [immMDTs]). However, published information on the composition and function of immMDTs is sparse, and there is little guidance for those seeking to establish or optimize an immMDT. To inform this review, we assembled a panel of 24 pediatric providers from multiple specialties who actively participate in immMDTs to provide expert opinion. We also conducted a search of the available information on pediatric immMDTs from PubMed. Based on these insights, we summarize the structure and function of active immMDTs across the United States and focus on best practices and context-dependent solutions that may enable institutions with varying goals, patient populations, and resources to establish an immMDT.

Development and validation of a predictive model for diagnosing EBER-positive lymphoma-associated hemophagocytic lymphohistiocytosis

PURPOSE

This study aims to identify distinguishing factors between EBER-positive lymphoma-associated hemophagocytic lymphohistiocytosis and non-neoplastic EBV-associated hemophagocytic lymphohistiocytosis. Additionally, we developed and validated a predictive diagnostic model based on these factors.

METHODS

To evaluate the early identification of individuals with EBER-positive lymphoma-associated hemophagocytic lymphohistiocytosis versus non-neoplastic EBV-associated hemophagocytic lymphohistiocytosis, we carried out a retrospective cohort research. The medical records system included 148 individuals' diagnoses of EBV-associated hemophagocytic lymphohistiocytosis between 2015 and 2023.

RESULTS

In this study, 148 patients were included, 75 of whom had non-neoplastic EBV-associated hemophagocytic lymphohistiocytosis and the remaining 73 had EBER-positive lymphoma-associated hemophagocytic lymphohistiocytosis. The highest AUC, with a good predictive value, was found for IL-10 > 39.87 pg/ml in separating EBER-positive lymphoma-associated hemophagocytic lymphohistiocytosis from non-neoplastic EBV-associated hemophagocytic lymphohistiocytosis. The diagnosis of EBER-positive lymphoma-associated hemophagocytic lymphohistiocytosis was influenced by platelets < 33.5*109/L, IL-6 > 20.79 pg/ml, and IFN-γ > 12.12 pg/ml as independent variables. These factors were combined with the predictive value of IL-10 > 39.87 pg/ml to establish the predictive model of the nomogram for diagnosis. The training set's and validation set's areas under the ROC curves were 0.825 and 0.812, respectively, showing that the model had good discrimination, a well-calibrated model, and a clinically valid model as indicated by the clinical decision curve.

CONCLUSION

The results of this study showed that the prediction model based on platelets < 33.5*109/L, IL-6 > 20.79 pg/ml, IFN-γ > 12.12 pg/ml, and IL-10 > 39.87 pg/ml could more accurately distinguish between EBER-positive lymphoma-associated hemophagocytic lymphohistiocytosis and non-neoplastic EBV-associated hemophagocytic lymphohistiocytosis. This could aid clinicians in the early detection and convenient individualization of treatment for EBV-associated hemophagocytic lymphohistiocytosis.

Diagnostic accuracy of bone marrow blood evaluation in haemophagocytic lymphohistiocytosis paediatric patients

IntroductionHaemophagocytic lymphohistiocytosis (HLH) is a rare and serious immunological syndrome that involves a strong activation of cytotoxic T lymphocytes and macrophages. HLH determines a cytokine-mediated tissue injury with a contemporary multi-organ failure and a high fatality rate.Material and methodsA retrospective study was performed considering the medical records of paediatric patients who underwent a bone marrow aspirate for suspect HLH. The biomarkers evaluated were among those included in the HLH-2004. Lactate dehydrogenase (LD) was also evaluated. Haemophagocytosis was evaluated in bone marrow blood smear slides.ResultsEnrolled were 11 patients included in the HLH group and 8 patients as controls. Haemoglobin and fibrinogen resulted lower in HLH patients than in controls, while blood triglycerides, serum ferritin and LD resulted increased. Blood triglycerides and fibrinogen discriminated HLH cases perfectly, with a sensitivity and specificity of 100%. Ferritin had a sensitivity of 100% and a specificity of 83% (cut off ≥3,721 µg/L) and LD of 73% and of 100% (the cut off ≥1,903 U/L). Haemoglobin was found to have a sensitivity of 75% and a specificity of 100% (cut off ≤ 96 g/L). Total haemophagocytes cell counts were not different between patients and controls. Only the increased number of phagocytized nucleated red blood cells (NRBC) was found to be significantly increased in the patients. Erythrocytes phagocytosis (≥4/1,000 cells) only tended towards significance.ConclusionsThe blood biomarkers showed better diagnostic performance than the morphological evaluation. Among the different cell lineages engulfed by haemophagocytes, the best diagnostic performance was obtained by phagocytosed mature erythrocytes and immature nucleated erythrocytes.

Hemophagocytic Lymphohistiocytosis with Predominant T-Lymphocytes in Young Child: An Unusual Presentation of Evolving Acute Myeloid Leukemia

Background: Hemophagocytic lymphohistiocytosis (HLH) is an aggressive, life-threatening condition commonly observed in young children. Distinguishing primary HLH from secondary HLH, such as malignancy-associated HLH, can be challenging, potentially leading to misdiagnosis and inappropriate treatment. Case presentation: A 16-month-old female presented with fever, decreased appetite, and rhinorrhea. A review of the peripheral blood smear revealed anemia and leukopenia, with absolute neutropenia characterized by a high lymphocyte count (approximately 80% were T cells by flow cytometry). Flow cytometry was negative for immunophenotypically abnormal cells. Initially, the cytopenia was attributed to a viral infection. However, the cytopenia did not improve, and a bone marrow evaluation revealed evidence of HLH but no immunophenotypically abnormal population. An extensive work-up for HLH, including next-generation sequencing (NGS) and cytogenetic testing identified the KMT2A::MLLT3 fusion transcript, indicating malignancy-associated HLH in the setting of evolving leukemia. Because there was no increase in blasts or immunophenotypically abnormal cells, the diagnosis of leukemia could not be made at that time. The patient was closely monitored and, seven weeks later, was diagnosed with acute myeloid leukemia/acute monocytic leukemia. In addition to the KMT2A::MLLT3 fusion, pathogenic variants in the PTPN11 and FLT3 genes were detected by NGS. Conclusions: The presentation of evolving acute monocytic leukemia can be nonspecific, mimicking conditions such as HLH, without an initial increase in immature cells or monocytes. Maintaining a broad differential diagnosis and including comprehensive molecular genetic testing may facilitate early diagnosis and appropriate treatment.

Extracorporeal Blood Purification in European Pediatric Intensive Care Units: A Consensus Statement

Importance

Important advances have been made in extracorporeal blood purification therapies (EBPTs) due to new technologies and biomaterials; however, the lack of established guidelines is a factor in great variability in clinical practice. This aspect is accentuated in pediatric intensive care given the small number of patients with diverse diagnoses treated with EBPT and the technical challenges in treating small children, potentiating the risk of adverse events.

Objective

To understand what experienced users of EBPT think about its relevant issues, insight that may have implications for the design of future studies, and the application of EBPTs in patient care.

Evidence Review

Literature search was conducted using the PubMed and Embase databases between January 1, 2020, and July 15, 2024, and a combination of key medical terms. A panel of experts was formed (composed of 15 authors and pediatric intensivists) to develop a consensus statement using a modified Delphi-based model between 2022 and 2024. The panel's core team drafted the initial questionnaire, which explored EBPT use in pediatric intensive care units (PICUs), including clinical indications for initiating and discontinuing use and outcomes for assessing effectiveness and safety. SurveyMonkey was used in the distribution, completion, and revision of the questionnaire, and findings were analyzed. Panelists were asked to rank answer choices. Numerical value for each ranking was translated to a percentage defining the strength of consensus (>90% agreement from panelists signifying strong consensus; <49% signifying no consensus).

Findings

A total of 116 survey responses were received from panelists from 8 European countries. Strong consensus was achieved on 6 of 24 questions and consensus (75%-90% agreement) was reached on 18 of 24 questions. According to the panelists, the continuous renal replacement therapy standard or enhanced adsorption hemofilter and plasma exchange were of interest, representing the most applied EBPTs across various applications. While evidence on hemoadsorption is growing, it remains limited.

Conclusions and Relevance

This consensus statement on EBPTs in critically ill pediatric patients was developed by an international panel of experts in areas where clinical evidence is still limited. This consensus statement could support pediatric intensivists in bedside decision-making and guide future research on EBPTs in PICUs.

Development of a Scoring Model to Predict Severe Dengue in Children at Admission to Emergency Care: An Observational Study

OBJECTIVE

Dengue has emerged as the most widely spread mosquito-borne disease, hyperendemic in India. Although severe dengue occurs only in a small proportion of cases, delays in the recognition and management can result in significant morbidity and mortality. Risk stratification of children in the emergency care and identifying those at risk for worsening during hospital stay facilitates optimum utilization of health care resources. The objective of our study was to develop and validate a scoring model to predict the development of severe dengue in hospitalized children by identifying risk factors present in them at the time of admission to the emergency department.

METHODS

A retrospective study of consecutive children aged 1 month to 18 years admitted with serologically confirmed dengue from January 2019 through December 2021 was conducted. Analysis of clinical and laboratory parameters of children resulted in the development of a comprehensive predictive scoring model. This model was internally validated prospectively on 107 children presenting with nonsevere dengue to emergency care.

RESULTS

A total of 743 children with confirmed dengue were studied out of which 216 (29.1%) had severe dengue. Presence of third spacing (odds ratio [OR] 3.74, 95% confidence interval [CI] 1.088-7.42, P < 0.001), tender hepatomegaly (OR 1.62, 95% CI 1.04-2.52, P < 0.032), respiratory distress (OR 3.50, 95% CI 1.89-6.51, P < 0.001), and moderate (OR 3.51, 95% CI 1.82-6.74, P < 0.001) to severe (OR 4.76, 95% CI 2.59-8.76, P < 0.001) elevation of aspartate aminotransferase were independent risk factors found to be associated with development of severe dengue. A score ≥7 had a specificity of 87%, negative predictive value of 86%, and overall diagnostic accuracy of 78.5% for predicting severe dengue.

CONCLUSIONS

The dengue severity scoring model was found to have reasonable diagnostic accuracy in predicting severe disease prior to hospitalization. However, more studies are required to validate the score in different emergency care settings with varied pediatric populations.

Unveiling Hyperinflammation in Severe Dengue With Coinfection Among Children: A Case Series

Dengue illness follows three phases: febrile, critical, and convalescent. Coinfection and hyperinflammatory response are common causes of the persistence of fever beyond the febrile phase of dengue. However, finding both these causes together in severe dengue cases is rarely reported in the literature. We present three cases of severe dengue who presented with persistent fever. The first case is of a 14-year-old girl who presented with dengue shock and culture-proven Acinetobacter sepsis. Later she was diagnosed with a hyperinflammatory response to infection and improved after intravenous immunoglobulin (IVIG) administration. The second case is of a 13-year-old boy who presented with severe dengue and culture-proven Burkholderia sepsis. He also had persistent fever despite appropriate treatment of infection which later improved after IVIG administration for hyperinflammation. The third case is of a 10-year-old girl who presented with severe dengue and encephalopathy. She was later diagnosed with coinfection with Japanese encephalitis and hyperinflammation. These cases highlighted that coinfection and hyperinflammatory response can both together complicate dengue infection.

Emapalumab in Patients With Macrophage Activation Syndrome Associated With Still's Disease: A Population Pharmacokinetic/Pharmacodynamic Analysis

Macrophage activation syndrome (MAS) is a life-threatening form of secondary haemophagocytic lymphohistiocytosis (HLH) associated with rheumatic diseases, most commonly Still's disease. This study aimed to develop a population pharmacokinetic (PK)/pharmacodynamic (PD) model for emapalumab, a fully human monoclonal antibody that targets interferon-gamma (IFNγ), in patients with MAS associated with Still's disease. A two-compartment disposition model based on data from patients with primary HLH administered emapalumab (1 mg/kg every 3 days, with possible increases to 3, 6 or 10 mg/kg) was re-estimated for patients with MAS administered emapalumab (6 mg/kg, then 3 mg/kg every 3 days until day 15 and twice weekly until day 28). An exploratory population PK/PD analysis comprising patients' PD data for total IFNγ, chemokine C-X-C motif ligand 9 (CXCL9) and ferritin was performed. Emapalumab clearance was generally linear and independent of total IFNγ levels in patients with MAS (n = 14). Estimated baseline levels of CXCL9 (a marker of IFNγ activity), soluble interleukin-2 receptor α (sIL-2Rα; a marker of hyperinflammation) and ferritin (a clinical marker of MAS disease activity) were 8400, 6550 and 15,300 μg/L, respectively. All three PD markers responded rapidly to changes in emapalumab concentration. Emapalumab almost completely suppressed CXCL9, sIL2-Rα, and ferritin production (estimated reduction in synthesis rate: 98.3%, 87%, and 99.6%, respectively). Population PK/PD modeling indicated that emapalumab rapidly suppresses markers of hyperinflammation in patients with MAS associated with Still's disease. Emapalumab dosing regimen used in clinical trials in patients with MAS is unlikely to need adjustment.

Hemophagocytic lymphohistiocytosis in early pregnancy: A rare and fatal diagnostic challenge

Objective

This report details the complexities of diagnosing and treating rapid-onset multisystemic hemophagocytic lymphohistiocytosis (HLH) during pregnancy, as evidenced by a fatal case in early pregnancy with severe hematological and obstetric complications.

Case presentation

A 20-year-old pregnant woman in her second pregnancy presented at 8 weeks of gestation with abdominal pain, fever, and rectal bleeding. Laboratory tests revealed leukopenia, thrombocytopenia, and anemia, leading to immediate transfusion and intensive care unit admission. Despite intensive interventions, including vasopressors and antibiotics, the patient developed progressive organ failure, with disseminated intravascular coagulation, and suffered a fatal stroke.

Conclusions

This critical case with severe complications demonstrates the diagnostic and treatment challenges of rapid-onset HLH in early pregnancy. Early and accurate differential diagnosis in obstetric emergencies is vital for conditions such as HLH. This case highlights the importance of multifaceted care in managing pregnant patients with complex, atypical presentations.

Risk Factors of Hemophagocytic Lymphohistiocytosis in Adults with Fever of Unknown Origin: A Retrospective Study

Purpose

Hemophagocytic lymphohistiocytosis (HLH) is a critical syndrome with a high mortality rate. In clinical practice, some patients with fever of unknown origin (FUO) can develop HLH, further complicating the diagnosis and treatment. However, studies on HLH in adults with FUO are limited. This study aimed to investigate the clinical characteristics of adult patients with FUO to facilitate the early identification of those at high risk of developing HLH.

Patients and Methods

We collected data from hospitalized patients with FUO between January 2014 and December 2020. Risk factors for HLH in adults with FUO were analyzed using univariate and multivariate analysis.

Results

A total of 988 patients with FUO were included in the study. The incidence of HLH in adults with FUO was 6.4%, with hematological tumors being the primary cause. Multivariate analysis indicated that skin rash and elevated alanine aminotransferase, total bilirubin, triglycerides, lactate dehydrogenase, and ferritin levels were independent risk factors for HLH in adults with FUO.

Conclusion

This study revealed the incidence rate, etiology distribution, and risk factors for HLH in adults with FUO. Comprehensive assessment of clinical and laboratory data at admission can assist in the early identification of FUO patients at risk for HLH.

Thrombocytopenia in Critically Ill Children: A Review for Practicing Clinicians

Thrombocytopenia frequently occurs in patients before, during, and after admission to Pediatric Intensive Care Units (PICUs). In critically ill children, it is often due to multifactorial causes and can be a sign of significant organ dysfunction. This review summarizes the potential causes/mechanisms of thrombocytopenia in acutely ill children, their identification, and treatments, with special attention paid to septic patients. The mechanisms of thrombocytopenia include decreased production and sequestration, but the most common reason is increased destruction or consumption. This review specifically reviews and compares the presentation, pathogenesis, and treatment of disseminated intravascular coagulation (DIC) and the thrombotic microangiopathic spectrum (TMA), including thrombocytopenia-associated multiorgan failure (TAMOF), hemolytic uremic syndrome, and other diagnoses. The other etiologies discussed include HLH/MAS, immune thrombocytopenia, and dilutional thrombocytopenia. Finally, this review analyzes platelet transfusions, the various thresholds, and complications.

Hemophagocytic Lymphohistiocytosis in a Kidney Transplant Recipient: Case Report

Hemophagocytic lymphohistiocytosis is a potentially fatal multisystemic inflammatory syndrome that is better understood in the pediatric population. Consequently, the diagnostic criteria for adults still derives from studies conducted in the pediatric population. Several genetic mutations and secondary causes, including infections, autoimmunity, and malignancy, have been reported as significant actors in this condition, especially in adults. It is of the utmost importance to identify these triggers, as the treatment of this condition is largely dependent on addressing the underlying cause. Those who have undergone transplantation and whose immune response is already compromised are particularly susceptible to this condition. We present the case of a 74-year-old kidney transplant recipient who was admitted due to a persistent fever of unknown origin, pancytopenia, and splenomegaly. The patient was ultimately diagnosed with hemophagocytic lymphohistiocytosis in our hospital secondary to Epstein-Barr virus, aspergillosis, and leishmania infections. Targeted treatments for the aforementioned conditions led to the resolution of the syndrome and the recovery of the patient. Lymphohistiocytosis is a rare, albeit serious, condition that should be considered a differential diagnosis in the early stages of critical illness in transplant recipient patients. Doing so enables target treatments to be administered as soon as possible.

Hemophagocytic Lymphohistiocytosis Secondary to Non-Hodgkin Lymphoma: A Case Report

Hemophagocytic lymphohistiocytosis (HLH) is a severe hyperinflammatory syndrome characterized by uncontrolled immune activation, often associated with malignancy in adults. Early recognition and prompt initiation of treatment are crucial in managing this condition due to its rapid progression and poor prognosis. We report the case of a 75-year-old male with suspected lymphoproliferative disease who presented with clinical criteria compatible with HLH. Immediate treatment with dexamethasone led to rapid clinical improvement, and the patient was referred to hematology for continued management of the underlying disease. This case highlights the importance of constant clinical surveillance, early intervention, and the use of well-structured diagnostic tools in managing this syndrome in adults, where significant diagnostic and treatment challenges remain.

Increased ferritin, serum lactate dehydrogenase, and aspartate aminotransferase levels predict macrophage activation syndrome complicating systemic lupus erythematosus: a retrospective study

Background

This study aimed to assess the diagnosis of macrophage activation syndrome (MAS) at the onset of active childhood-onset systemic lupus erythematosus (cSLE), which is under-researched, and to compare the characteristics of cSLE with and without MAS, hypothesizing the existence of possible predictors of MAS in active cSLE.

Methods

This study enrolled 157 patients diagnosed with cSLE, with or without MAS, from Nanjing Medical University between January 2018 and May 2023. Data analysis was performed using an independent samples t-test or the Mann-Whitney U-test, the χ 2 test, the Youden index to determine the optimal cutoff values for diagnosis, and binary logistic regression analysis to determine the predicted probability.

Results

Fifteen patients (9%) had MAS in the active phase, with an SLE disease activity index of 16.6 (range, 6-32). Bone marrow aspirations revealed hemophagocytosis in 8/15 cases (53%). Fever was the most common feature of MAS patients. Lactate dehydrogenase (LDH) and ferritin levels were elevated in the patients. Lower leukocyte, neutrophil, and platelet counts, including serum sodium and fibrinogen, and increased alanine aminotransferase, aspartate aminotransferase (AST), lactate dehydrogenase (LDH), ferritin, triglyceride, and D-dimer levels occurred in MAS patients, unlike those without MAS. Optimal cutoff values for ferritin (≥607.35 ng/ml), LDH (≥424 U/L), and AST (≥61 U/L) were predictors of MAS occurrence in cSLE. No MAS patients experienced recurrence during an 18-month mean follow-up.

Conclusions

Despite the narrow scope of the study, elevated levels of ferritin, LDH, and AST may represent indicators of cSLE complicated by MAS. Early diagnosis and treatment may improve outcomes.

Prognostic Impact of Aetiology in Adult Hemophagocytic Lymphohistiocytosis: Insights from an Intensive Care Unit Experience

Background

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening hyperinflammatory syndrome marked by excessive immune activation. It can be triggered by various factors, including infections, malignancies, and autoimmune diseases, making the diagnosis challenging due to its overlap with other severe conditions.

Case reports

We discuss two intensive care unit (ICU) cases illustrating the diverse manifestations of HLH and the critical importance of early recognition and treatment. The first case involves natural killer-cell leukaemia, and the second, a suspected viral trigger. Both highlight the necessity of a multidisciplinary approach in diagnosis and management, emphasizing the complexity of HLH in ICU settings.

Conclusions

High mortality rates, particularly in malignancy-associated HLH, underscore the importance of tailored treatment strategies based on the underlying aetiology.

LEARNING POINTS

Hemophagocytic lymphohistiocytosis (HLH) in adults can arise from a variety of triggers, including infections and malignancies, each influencing disease progression and prognosis differently. Recognizing these underlying aetiologies is crucial for tailoring management strategies and anticipating clinical outcomes.Due to its life-threatening nature, HLH requires prompt diagnosis and a coordinated, multidisciplinary approach. Early intervention, incorporating immunosuppressive therapies and supportive care, is essential to improve patient outcomes, particularly in intensive care unit settings where disease severity is often pronounced.Utilizing diagnostic tools such as the HScore and HLH-2004 criteria can facilitate early identification of HLH in critically ill patients with unexplained inflammatory symptoms. These tools, along with a high index of suspicion, help distinguish HLH from other hyperinflammatory conditions, enabling timely and appropriate therapeutic interventions.

Macrophage activation syndrome in Sepsis: from pathogenesis to clinical management

BACKGROUND

Sepsis represents a significant global health and hygiene challenge. Excessive activation of macrophages in sepsis can result in certain patients displaying characteristics akin to those observed in Macrophage Activation Syndrome (MAS). MAS represents a grave immune system disorder characterized by persistent and severe inflammation within the body. In the context of sepsis, MAS presents atypically, leading some researchers to refer to it as Macrophage Activation-Like Syndrome (MALS). However, there are currently no effective treatment measures for this situation. The purpose of this article is to explore potential treatment methods for sepsis-associated MALS.

OBJECTIVE

The objective of this review is to synthesize the specific pathophysiological mechanisms and treatment strategies of MAS to investigate potential therapeutic approaches for sepsis-associated MALS.

METHOD

We searched major databases (including PubMed, Web of Science, and Google Scholar etc.) for literature encompassing macrophage activation syndrome and sepsis up to Mar 2024 and combined with studies found in the reference lists of the included studies.

CONCLUSION

We have synthesized the underlying pathophysiological mechanism of MALS in sepsis, and then summarized the diagnostic criteria and the effects of various treatment modalities utilized in patients with MAS or MALS. In both scenarios, heterogeneous treatment responses resulting from identical treatment approaches were observed. The determination of whether the patient is genuinely experiencing MALS significantly impacts the ultimate outcomes of therapeutic efficacy. In order to tackle this concern, additional clinical trials and research endeavors are imperative.

A Novel Engineering Cell Therapy Platform Mimicking the Immune Thrombocytopenia-Derived Platelets to Inhibit Cytokine Storm in Hemophagocytic Lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a common and highly fatal hyperinflammatory syndrome characterized by the aberrant activation of macrophages. To date, there is a lack of targeted therapies for HLH. It is validated that macrophages in HLH efficiently phagocytose anti-CD41-platelets (anti-CD41-PLTs) from immune thrombocytopenia (ITP) patients in previous research. Hence, the pathological mechanisms of ITP are mimicked and anti-CD41-PLTs are utilized to load the macrophage-toxic drug VP16 to construct macrophage-targetable engineered platelets anti-CD41-PLT-VP16, which is a novel targeted therapy against HLH. Both in vitro and in vivo studies demonstrate that anti-CD41-PLT-VP16 has excellent targeting and pro-macrophage apoptotic effects. In HLH model mice, anti-CD41-PLT-VP16 prevents hemophagocytosis and inhibits the cytokine storm. Mechanistic studies reveal that anti-CD41-PLT-VP16 increases the cytotoxicity of VP16, facilitating precise intervention in macrophages. Furthermore, it operates as a strategic "besieger" in diminishing hyperinflammation syndrome, which can indirectly prevent the abnormal activation of T cells and NK cells and reduce the Ab-dependent cell-mediated cytotoxicity effect. The first platelet-based clinical trial is ongoing. The results show that after treatment with anti-CD41-PLT-VP16, HLH patients have a threefold increase in the overall response rate compared to patients receiving conventional chemotherapy. In conclusion, anti-CD41-PLT-VP16 provides a general insight into hyperinflammation syndrome and offers a novel clinical therapeutic strategy for HLH.

Peripheral Axonal Neuropathy in Hemophagocytic Lymphohistiocytosis Secondary to Rickettsia conorii Infection

Hemophagocytic lymphohistiocytosis (HLH) is a rare and potentially fatal hyperinflammatory syndrome characterized by dysregulated immune activation and systemic inflammation. Secondary HLH is often triggered by infections, with Rickettsia conorii being an infrequently reported cause. Peripheral axonal neuropathy is a rare and poorly understood complication of HLH. We present the case of a 58-year-old male who presented with fever, diarrhea, a maculopapular rash involving the palms and soles, and progressive lower limb weakness. Laboratory findings revealed pancytopenia, hyperferritinemia, elevated soluble CD25, liver cytolysis, hypofibrinogenemia, and raised inflammatory markers. Serological testing confirmed Rickettsia conorii infection. The patient fulfilled six of the eight HLH-2004 diagnostic criteria, establishing the diagnosis of secondary HLH. Treatment was initiated with intravenous dexamethasone and doxycycline. During hospitalization, the patient developed severe hypoxemic respiratory failure, paraplegia, and acute sensory loss. The neurological evaluation confirmed peripheral axonal neuropathy linked to Rickettsia conorii infection, which preceded the development of HLH. After 21 days of doxycycline therapy, the patient was discharged to a rehabilitation facility with full neurological recovery. This case underscores the rarity of Rickettsia conorii as a trigger for HLH and highlights the exceptional occurrence of peripheral axonal neuropathy as a complication. The singularity of this case reinforces the importance of a correct and early diagnosis of HLH, which can have atypical and severe complications but also a successful outcome.

Hemophagocytic lymphohistiocytosis: current treatment advances, emerging targeted therapy and underlying mechanisms

Hemophagocytic lymphohistiocytosis (HLH) is a rapidly progressing, life-threatening syndrome characterized by excessive immune activation, often presenting as a complex cytokine storm. This hyperactive immune response can lead to multi-organ failure and systemic damage, resulting in an extremely short survival period if left untreated. Over the past decades, although HLH has garnered increasing attention from researchers, there have been few advancements in its treatment. The cytokine storm plays a crucial role in the treatment of HLH. Investigating the detailed mechanisms behind cytokine storms offers insights into targeted therapeutic approaches, potentially aiding in early intervention and improving the clinical outcome of HLH patients. To date, there is only one targeted therapy, emapalumab targeting interferon-γ, that has gained approval for primary HLH. This review aims to summarize the current treatment advances, emerging targeted therapeutics and underlying mechanisms of HLH, highlighting its newly discovered targets potentially involved in cytokine storms, which are expected to drive the development of novel treatments and offer fresh perspectives for future studies. Besides, multi-targeted combination therapy may be essential for disease control, but further trials are required to determine the optimal treatment mode for HLH.

Hemophagocytic lymphohistiocytosis caused by multiple infections during primary chemotherapy for pediatric acute lymphoblastic leukemia: a case report

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory disorder that occurs as a consequence of immune dysregulation. HLH can be primary (familial or non-familial) or secondary to infection, autoimmune disease or malignancy. Malignancy-associated HLH is often accompanied by hematologic and lymphoid neoplasms. This report describes the case of a 3-year-old girl with an initial diagnosis of acute lymphoblastic leukemia who subsequently developed HLH during primary chemotherapy. She was admitted with a pulmonary infection, and initial blood tests showed thrombocytopenia and anemia. Whole-exome sequencing of gene and whole transcriptome RNA sequencing data indicated mutations of UNC13D. The hospital course was complicated by multiple infections, altered mental status and acute respiratory distress syndrome. HLH secondary to multiple infections that achieved remission following targeted therapy with ruxolitinib, in conjunction with corticosteroids and other complementary treatments. This report provides a synopsis of the diagnostic and treatment procedures implemented in this case.

Pre-diagnostic trajectory of pediatric hemophagocytic lymphohistiocytosis: observations from hematological and hepatic parameters

Understanding the early features and characteristics of hemophagocytic lymphohistiocytosis (HLH) is essential for identifying high-risk individuals and also providing valuable pathological insights. This study aims to investigate the characteristics and trends of blood and hepatic parameters before an HLH diagnosis was established. Longitudinal hematological and hepatic test results from pediatric patients with HLH and an age- and sex-matched control group were analyzed. According to the length of time between hospital admission and the establishment of the HLH diagnosis, the HLH cases were divided into early-onset (≤ 7 days) and late-onset (> 7days) groups. Among the 229 pediatric HLH patients, the length of time between hospital admission and the establishment of an HLH diagnosis ranged from 0 to 41 days (median = 4 days). Over 80% of pediatric HLH patients presented abnormal laboratory results for aspartate aminotransferase (AST), triglycerides, lactate dehydrogenase (LDH), and hemoglobin at admission. The abnormal rates in the initial platelet count, neutrophil count, and fibrinogen tests were 67.3%, 48.3%, and 52.2%, respectively. The initial test results for AST, alanine aminotransferase (ALT), LDH, serum sodium, and albumin showed AUCs > 80% for discriminating early-onset HLH. For the discrimination of late-onset HLH, the performance of initial test results was poor. To conclude, abnormalities in AST, triglycerides, LDH, and hemoglobin are early presentations of pediatric HLH; platelet, neutrophil, and fibrinogen levels may become abnormal at a relatively late stage of the HLH disease trajectory; and the initial test results for AST, ALT, LDH, serum sodium, and albumin can be used to identify suspected early-onset HLH.

Intravenous Anakinra for Treating Macrophage Activation Syndrome in Adult-Onset Still's Disease

Background

Adult-onset Still's disease (AOSD) is a rare systemic inflammatory disease characterized by fever, rash, arthritis, and multi-organ involvement. Macrophage activation syndrome (MAS), a serious complication of AOSD, poses significant diagnostic and therapeutic challenges.

Case Presentation

A 32-year-old male was diagnosed with AOSD in 2020 after being hospitalized for a fever of unknown origin and elevated liver enzymes. The patient was initially treated with corticosteroids and methotrexate but subsequently discontinued both treatment and follow-up. In September 2023, he presented with fever, sore throat, and elevated inflammatory markers. After screening for infections, methylprednisolone (MP) treatment was initiated because of AOSD activation. The following day, the patient was admitted to the intensive care unit due to an altered state of consciousness. Brain magnetic resonance imaging revealed brainstem involvement. Empirical treatments were initiated, including intravenous MP, and immunoglobulin therapy. Due to suspected macrophage activation syndrome (MAS), anakinra (ANA) infusion was initiated. Significant improvement was observed after the ANA infusion.

Conclusion

This case highlights the complex management of severe AOSD complications, emphasizing the role of early recognition, aggressive therapy, and multidisciplinary care in improving outcomes.

LEARNING POINTS

Macrophage activation syndrome (MAS) is a serious complication of adult-onset Still's disease characterized by systemic inflammation. Early recognition and prompt initiation of treatment are crucial due to the high mortality rate associated with MAS, especially when neurologic symptoms are present.Clinicians should not delay treatment pending confirmatory diagnostic tests when MAS is suspected, as early intervention can significantly impact patient outcomes.Anakinra, an interleukin-1 inhibitor, is typically administered subcutaneously but has shown promise when administered intravenously, particularly in severe cases of MAS.

Predicting relapsed/refractory disease in childhood hemophagocytic lymphohistiocytosis based on clinical features at diagnosis: A 13-year single-institute retrospective study in Thailand

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening disease. Relapsed/refractory disease is the main cause of death. This study aims to determine the prognostic indicators for relapsed/refractory disease in childhood HLH (R/R HLH). Infants and children under 18 years of age who were diagnosed with HLH according to HLH-2004 criteria, MAS-HLH criteria for rheumatologic diseases, or H-score undergoing treatment in Chiang Mai University hospital between 2010 and 2022 were included. Demographic data, clinical characteristics, and laboratory parameters were retrospectively reviewed. Out of 86 childhood HLH cases, 30 patients (34.9%) experienced R/R HLH. All patients with primary HLH developed R/R HLH. The most common form of secondary HLH was infection-associated hemophagocytic syndrome (IAHS), comprising 43 cases. Of these, 37.2% had relapsed or refractory disease. Univariable analysis identified several potential risk factors for R/R HLH, including younger age, severe disease status, higher HLH-2004 criteria scores, higher H-scores, overt DIC, higher pSOFA scores, and increased levels of aspartate aminotransferase, total bilirubin, and direct bilirubin. Multivariable logistic regression analysis revealed that a pSOFA score of ≥ 8 and age < 3 years were independent risk factors for R/R HLH, with adjusted odds ratios of 6.35 (95% confidence interval [CI], 1.18-34.19; P = 0.032) and 3.62 (95% CI, 1.04-12.63; P = 0.044), respectively. Children with HLH who have a pSOFA score of ≥ 8, or are younger than 3 years, are at a higher risk of relapsed or refractory disease. Further evaluation of management strategies in this context is warranted.

Interleukin-1-mediated hyperinflammation in XIAP deficiency is associated with defective autophagy

ABSTRACT

Deficiency of X-linked inhibitor of apoptosis protein (XIAP) is a rare genetic condition that can present with recurrent episodes of hemophagocytic lymphohistiocytosis (HLH), though the exact mechanisms leading to this hyperinflammatory disorder are unclear. Understanding its biology is critical to developing targeted therapies for this potentially fatal disease. Here, we report on a novel multiexonic intragenic duplication leading to XIAP deficiency with recurrent HLH that demonstrated complete response to interleukin (IL)-1β blockade. We further demonstrate using both primary patient cells and genetically modified THP-1 monocyte cell lines that, contrary to what has previously been shown in mouse cells, XIAP-deficient human macrophages do not produce excess IL-1β when stimulated under standard conditions. Instead, nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-mediated hyperproduction of IL-1β is observed only when the XIAP-deficient cells are stimulated under autophagy-promoting conditions and this correlates with defective autophagic flux as measured by decreased accumulation of the early autophagy marker LC3-II. This work, therefore, highlights IL-1β blockade as a therapeutic option for patients with XIAP deficiency experiencing recurrent HLH and identifies a critical role for XIAP in promoting autophagy as a means of limiting IL-1β-mediated hyperinflammation during periods of cellular stress.

Breaking the storm: ruxolitinib as a lifeline in refractory hemophagocytic lymphohistiocytosis with macrophage activation syndrome

This case report presents the management of a 25-year-old woman with refractory hemophagocytic lymphohistiocytosis (HLH) secondary to adult-onset Still's disease. Despite initial treatment with corticosteroids and biologic therapies, including anakinra and tocilizumab, her condition continued to deteriorate, necessitating intensive care unit admission. Following multidisciplinary consultation, ruxolitinib therapy, a Janus kinase (JAK) inhibitor targeting hyperinflammation, was initiated. Remarkably, the patient exhibited significant clinical improvement with resolution of fever, normalization of inflammatory markers, and organ function recovery. This case underscores the potential of ruxolitinib as a therapeutic option in refractory cases of HLH or macrophage activation syndrome, highlighting the importance of exploring novel therapies in refractory and challenging clinical scenarios.

Acute kidney injury in critical care: complications of hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is an immune dysfunction characterized by an exaggerated and pathological inflammatory response, potentially leading to systemic inflammatory reactions and multiple-organ failure, including renal involvement. HLH can be classified as primary or secondary, with primary HLH associated with genetic mutations affecting cell degranulation capacity, and secondary HLH often linked to infections, tumors, and autoimmune diseases. The pathogenesis of HLH is not fully understood, but primary HLH is typically driven by genetic defects, whereas secondary HLH involves the activation of CD8+ T cells and macrophages, leading to the release of inflammatory cytokines and systemic inflammatory response syndrome (SIRS). The clinical presentation of HLH includes non-specific manifestations, making it challenging to differentiate from severe sepsis, particularly secondary HLH due to infections. Shared features include prolonged fever, hepatosplenomegaly, hematopenia, hepatic dysfunction, hypertriglyceridemia, and hypofibrinogenemia, along with histiocytosis and hemophagocytosis. However, distinctive markers like dual hemocytopenia, hypertriglyceridemia, hypofibrinogenemia, and elevated sCD25 levels may aid in differentiating HLH from sepsis. Indeed, no singular biomarker effectively distinguishes between hemophagocytic lymphohistiocytosis and infection. However, research on combined biomarkers provides insights into the differential diagnosis. Renal impairment is frequently encountered in both HLH and sepsis. It can result from a systemic inflammatory response triggered by an influx of inflammatory mediators, from direct damage caused by these factors, or as a consequence of the primary disease process. For instance, macrophage infiltration of the kidney can lead to structural damage affecting various renal components, precipitating disease. Presently, tubular necrosis remains the predominant form of renal involvement in HLH-associated acute kidney injury (HLH-AKI). However, histopathological changes may also encompass interstitial inflammation, glomerular abnormalities, microscopic lesions, and thrombotic microangiopathy. Treatment approaches for HLH and sepsis diverge significantly. HLH is primarily managed with repeated chemotherapy to eliminate immune-activating stimuli and suppress hypercellularity. The treatment approach for sepsis primarily focuses on anti-infective therapy and intensive symptomatic supportive care. Renal function significantly influences clinical decision-making, particularly regarding the selection of chemotherapy and antibiotic dosages, which can profoundly impact patient prognosis. Conversely, renal function recovery is a complex process influenced by factors such as disease severity, timely diagnosis, and the intensity of treatment. A crucial aspect in managing HLH-AKI is the timely diagnosis, which plays a pivotal role in reversing renal impairment and creating a therapeutic window for intervention, may have opportunity to improve patient prognosis. Understanding the clinical characteristics, underlying causes, biomarkers, immunopathogenesis, and treatment options for hemophagocytic lymphohistiocytosis associated with acute kidney injury (HLH-AKI) is crucial for improving patient prognosis.

Population Pharmacokinetics of the Anti-Interferon-Gamma Monoclonal Antibody Emapalumab: An Updated Analysis

INTRODUCTION

Emapalumab is a fully human monoclonal antibody that targets free and receptor-bound interferon-gamma (IFNγ), neutralizing its biological activity. IFNγ levels differ by orders of magnitude between patients with primary hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS; a form of secondary HLH) in systemic juvenile idiopathic arthritis (sJIA). Therefore, this study aimed to develop a population pharmacokinetic model for emapalumab across a patient population with a wide range of total (free and emapalumab-bound) IFNγ levels using observations from patients with primary HLH or MAS in sJIA in clinical trials.

METHODS

Pharmacokinetic data were pooled (n = 58; 2709 observations) from studies enrolling patients administered emapalumab for primary HLH or MAS in sJIA. Patients with primary HLH were administered emapalumab 1 mg/kg (potentially increasing to 3, 6, and up to 10 mg/kg based on clinical response) every 3 days. Patients with MAS in sJIA were administered emapalumab 6 mg/kg, followed by 3 mg/kg every 3 days until day 15 and twice weekly until day 28. An earlier population PK model was re-parameterized using this data.

RESULTS

The final model for emapalumab comprised a 2-compartment model with first-order elimination. Emapalumab clearance remains constant when the total IFNγ concentration (free and emapalumab-bound) is < ~ 10,000 pg/ml but increases proportionally to total IFNγ concentration above this threshold. Emapalumab clearance was estimated to be 0.00218, 0.00308, 0.00623 and 0.01718 l/h at total serum IFNγ concentrations of 103, 104, 105 and 106 pg/ml, respectively, with corresponding terminal half-lives of 19.2, 13.8, 7.18 and 3.12 days for a 1-year-old patient weighing 10 kg with primary HLH. The median terminal half-life for emapalumab in patients with MAS in sJIA was estimated to be 24.0 (range, 6.13-32.4) days, which is similar to observations in healthy volunteers.

CONCLUSIONS

Emapalumab pharmacokinetics in patients with primary HLH and MAS in sJIA were described by a two-compartment model with fixed allometric exponents and an age-related effect. Differences in total IFNγ levels between patients with primary HLH and MAS may affect emapalumab pharmacokinetics, suggesting that each indication may require different dosing to rapidly control hyperinflammation.

TRIAL REGISTRATION

Clinicaltrials.gov identifiers: NCT01818492, NCT03311854 and NCT02069899.

Navigating the Complexity: A Comprehensive Review of Hemophagocytic Lymphohistiocytosis Associated With Dengue Infection

Hemophagocytic lymphohistiocytosis (HLH) associated with dengue infection presents a unique challenge in clinical practice due to its rarity, rapid progression, and overlapping clinical features. This comprehensive review navigates the complexity of HLH-dengue syndrome by examining its pathophysiology, clinical manifestations, diagnostic criteria, and therapeutic strategies. HLH, characterized by uncontrolled immune activation and cytokine dysregulation, can occur as a secondary complication of dengue infection, leading to severe multiorgan dysfunction and high mortality if not promptly recognized and treated. The review underscores the significance of early diagnosis through vigilant clinical monitoring and appropriate diagnostic tests, such as bone marrow examinations and genetic studies. Collaboration between infectious disease specialists, hematologists, and critical care teams is essential for optimal management. Despite advancements in understanding HLH-dengue syndrome, further research is needed to elucidate its underlying mechanisms and explore novel treatment approaches. This review provides insights into the clinical implications of HLH-dengue syndrome and emphasizes the importance of a multidisciplinary approach to improve patient outcomes in this challenging clinical scenario.

Dengue-Associated Hemophagocytic Lymphohistiocytosis: A Narrative Review of Its Identification and Treatment

Dengue's lack of specific treatments beyond supportive care prompts a focus on uncovering additional pathophysiological factors. Dengue-associated hemophagocytic lymphohistiocytosis (HLH), characterized by dysregulated macrophage activation and cytokine storm, remains underexplored despite its potential to worsen disease severity and mortality. While rare, dengue-associated HLH disproportionately affects severe cases, significantly impacting mortality rates. To mitigate high mortality, early identification and familiarity with dengue-associated HLH are imperative for prompt treatment by clinicians. This narrative review therefore aims to examine the current clinical and therapeutic knowledge on dengue-associated HLH, and act as a resource for clinicians to improve their management of HLH associated with severe dengue. Dengue-associated HLH should be considered for all cases of severe dengue and may be suspected based on the presence of prolonged or recurrent fever for >7 days, or anemia without intravascular hemolysis or massive bleeding. Diagnosis relies on fulfilling at least five of the eight HLH-2004 criteria. Treatment predominantly involves short courses (3-4 days) of high-dose steroids (e.g., dexamethasone 10 mg/m2), with additional therapies considered in more severe presentations. Notably, outcomes can be favorable with steroid therapy alone.

Cardiac Involvement in Patients With Multisystem Inflammatory Syndrome in Adults

Multisystemic inflammatory syndrome in adults is a hyperinflammatory condition following (within 4-12 weeks) SARS-CoV-2 infection. Here, the dysregulation of the immune system leads to a multiorgan involvement often affecting the heart. Cardiac involvement in multisystemic inflammatory syndrome in adults has been described mainly in young men without other comorbidities and may present with different clinical scenarios, including acute heart failure, life-threatening arrhythmias, pericarditis, and myocarditis, with a nonnegligible risk of mortality (up to 7% of all cases). The heterogeneity of its clinical features and the absence of a clear case definition make the differential diagnosis with other postinfectious (eg, infective myocarditis) and hyperinflammatory diseases (eg, adult Still disease and macrophage activation syndrome) challenging. Moreover, the evidence on the efficacy of specific treatments targeting the hyperinflammatory response underlying this clinical condition (eg, glucocorticoids, immunoglobulins, and other immunomodulatory agents) is sparse and not supported by randomized clinical trials. In this review article, we aim to provide an overview of the clinical features and the diagnostic workup of multisystemic inflammatory syndrome in adults with cardiac involvement, highlighting the possible pathogenetic mechanisms and the therapeutic management, along with remaining knowledge gaps in this field.

Lymphoma-associated hemophagocytic lymphohistiocytosis (LA-HLH): a scoping review unveils clinical and diagnostic patterns of a lymphoma subgroup with poor prognosis

Hemophagocytic lymphohistiocytosis (HLH) is a severe hyperinflammatory syndrome driven by pathologic activation of cytotoxic T-lymphocytes and macrophages. Despite advances in diagnostics and management, adult patients with lymphoma-associated HLH (LA-HLH) harbor particularly poor prognosis and optimal treatment remains challenging. As systematic data on LA-HLH are scarce, we aimed to synthesize research evidence by thorough analysis of the published literature in PubMed (MEDLINE-database) within the context of a scoping review. Of 595 search results, 132 articles providing information on 542 patients were reviewed and analyzed. Median patient age was 60 years (range, 18-98) with male predominance (62.7%). B- and T-NHL were equally represented (45.6% and 45.2%), Hodgkin's lymphoma was reported in 8.9% of the cases. The majority of patients (91.6%) presented in Ann-Arbor-Stages III and IV, and bone marrow infiltration was observed in a significant proportion of patients (61.5%). Soluble CD25 levels were markedly elevated (median 10,000 U/ml), with levels beyond 10,000 U/ml indicating unfavorable prognosis for 30-day and overall survival. 66.8% of the patients died after median 5.1 months. LA-HLH remains a clinical challenge requiring specialized management. Timely diagnosis and appropriate lymphoma-specific treatment are of utmost importance to enhance patient outcomes.

Malignancy-associated hemophagocytic lymphohistiocytosis in Sweden: incidence, clinical characteristics, and survival

ABSTRACT

We evaluated malignancy-associated hemophagocytic lymphohistiocytosis (mal-HLH) in Sweden regarding population-based incidence, clinical features, and survival. From 1997 to 2018, we identified 307 adults (≥18 years old) and 9 children (209 males, 107 females; P < .001) with both an HLH-related diagnosis and malignant disease, corresponding to 0.19 per 100 000 adults annually (0.15/100 000 for the entire population), increasing from 0.026 (1997-2007) to 0.34 (2008-2018) (P < .001). In the latest 7-year period (2012-2018), the annual incidence was 0.45 per 100 000 adults (n = 246). This incidence varied between the 6 health care regions in Sweden, from 0.18 to 0.71 (Region Stockholm) per 100 000 adults annually (P < .001), likely due to variable awareness. Mal-HLH was reported in 0.6% of all hematological malignancies, with the highest proportion (2.5%) in young males. Among the 316 patients, the 1-month probability of survival, likely representing the HLH episode, increased significantly from 52% (95% confidence interval [CI], 40-63) (1997-2007) to 71% (95% CI, 65-76) (2008-2018), whereas 2-year survival remained poor (25%; 95% CI, 20-30). Altogether, 52% were lymphomas, 29% leukemias, 8% other hematological malignancies, and 11% solid tumors. Males were more affected than females by mal-HLH, also taking the over-representation of males with hematological malignancies into account (P = .0012). Validation by medical-file reviews revealed 13% over-reporting of HLH. We conclude that the annual mal-HLH incidence has increased 10-fold and was at least 0.71 per 100 000 adults from 2012 to 2018, that is, 0.62 per 100 000 adults considering 13% estimated HLH over-reporting, and that early survival improved significantly, likely due to increased awareness and more HLH-directed therapy.

Laboratory Features and Pathology of Cytokine Storm Syndromes

The laboratory diagnosis of cytokine storm syndromes (CSSs), i.e., hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS), is often challenging. The laboratory features using routinely available tests lack specificity, whereas confirmatory testing is available in only few laboratories in the United States. The disease mechanisms are still largely unclear, particularly in adults. In this chapter, the pathogenesis of CSSs, their associated laboratory findings, and recommended diagnostic strategies are reviewed.

Severe dengue in the intensive care unit

Dengue fever is considered the most prolific vector-borne disease in the world, with its transmission rate increasing more than eight times in the last two decades. While most cases present mild to moderate symptoms, 5% of patients can develop severe disease. Although the mechanisms are yet not fully comprehended, immune-mediated activation leading to excessive cytokine expression is suggested as a cause of the two main findings in critical patients: increased vascular permeability that may shock and thrombocytopenia, and coagulopathy that can induce hemorrhage. The risk factors of severe disease include previous infection by a different serotype, specific genotypes associated with more efficient replication, certain genetic polymorphisms, and comorbidities such as diabetes, obesity, and cardiovascular disease. The World Health Organization recommends careful monitoring and prompt hospitalization of patients with warning signs or propensity for severe disease to reduce mortality. This review aims to update the diagnosis and management of patients with severe dengue in the intensive care unit.

Cytokine Storm and Sepsis-Induced Multiple Organ Dysfunction Syndrome

There is extensive overlap of clinical features among familial or primary HLH (pHLH), reactive or secondary hemophagocytic lymphohistiocytosis (sHLH) [including macrophage activation syndrome (MAS) related to rheumatic diseases], and hyperferritinemic sepsis-induced multiple organ dysfunction syndrome (MODS); however, the distinctive pathobiology that causes hyperinflammatory process in each condition requires careful considerations for therapeutic decision-making. pHLH is defined by five or more of eight HLH-2004 criteria [1], where genetic impairment of natural killer (NK) cells or CD8+ cytolytic T cells results in interferon gamma (IFN-γ)-induced hyperinflammation regardless of triggering factors. Cytolytic treatments (e.g., etoposide) or anti-IFN-γ monoclonal antibody (emapalumab) has been effectively used to bridge the affected patients to hematopoietic stem cell transplant. Secondary forms of HLH also have normal NK cell number with decreased cytolytic function of varying degrees depending on the underlying and triggering factors. Although etoposide was uniformly used in sHLH/MAS in the past, the treatment strategy in different types of sHLH/MAS is increasingly streamlined to reflect the triggering/predisposing conditions, severity/progression, and comorbidities. Accordingly, in hyperferritinemic sepsis, the combination of hepatobiliary dysfunction (HBD) and disseminated intravascular coagulation (DIC) reflects reticuloendothelial system dysfunction and defines sepsis-associated MAS. It is demonstrated that as the innate immune response to infectious organism prolongs, it results in reduction in T cells and NK cells with subsequent lymphopenia even though normal cytolytic activity continues (Figs. 30.1, 30.2, 30.3, and 30.4). These changes allow free hemoglobin and pathogens to stimulate inflammasome activation in the absence of interferon-γ (IFN-γ) production that often responds to source control, intravenous immunoglobulin (IVIg), plasma exchange, and interleukin 1 receptor antagonist (IL-1Ra), similar to non-EBV, infection-induced HLH.

Etoposide Therapy of Cytokine Storm Syndromes

Etoposide has revolutionized the treatment of primary as well as secondary hemophagocytic lymphohistiocytosis (HLH), and it is, together with corticosteroids, the most widely used therapy for HLH. In the early 1980s, long-term survival in primary HLH was <5% but with the etoposide-/dexamethasone-based protocols HLH-94 and HLH-2004, in combination with stem cell transplantation, 5-year survival increased dramatically to around 60% in primary HLH, and based on analyses from the HLH-2004 study, there is likely room for further improvement. Biologically, etoposide administration results in potent selective deletion of activated T cells as well as efficient suppression of inflammatory cytokine production. Moreover, etoposide has also been reported to promote programmed cell death (apoptosis) rather than proinflammatory lytic cell death (pyroptosis), conceivably ameliorating subsequent systemic inflammation, i.e., a treatment very suitable for cytokine storm syndromes (CSS). The combination of etoposide and corticosteroids may also be beneficial in cases of severe or refractory secondary HLH (sHLH) with imminent organ failure, such as infection-associated HLH caused by Epstein-Barr virus (EBV) or malignancy-triggered HLH. In CSS associated with rheumatic diseases (macrophage activation syndrome, MAS or MAS-HLH), etoposide is currently used as second- or third-line therapy. Recent studies suggest that etoposide perhaps should be part of an aggressive therapeutic intervention for patients with severe refractory or relapsing MAS, in particular if there is CNS involvement. Importantly, awareness of sHLH must be further increased since treatment of sHLH is often delayed, thereby missing the window of opportunity for a timely, effective, and potentially life-saving HLH-directed treatment.

Iatrogenic HLH

Hemophagocytic lymphohistiocytosis (HLH) can be categorized as either primary (familial, generally occurring in infants) or secondary (sHLH, occurring at any age in association with a variety of conditions) and is mainly triggered by infections, autoimmune diseases, and malignant conditions. Our understanding of the pathophysiology of sHLH is still evolving, and among the causes and associations with the syndrome, those putatively associated with iatrogenic causes remain among the most poorly understood due to the rarity of these entities and the multiple confounders so often present in the patients in whom they are reported. Herein, we present a review of the literature to describe the diagnostic and therapeutic challenges of sHLH associated with iatrogenic causes and discuss some of the challenges and future directions in our efforts to better understand these complex conditions for the advancement of patient outcomes.

Inpatient recognition and management of HLH

Hemophagocytic lymphohistiocytosis (HLH) is one of the life-threatening emergencies that a hematologist may be called upon to diagnose and manage. It is a hyperinflammatory process that develops in patients with genetic abnormalities, hematologic malignancies, chronic inflammatory states, or infections. The main clinical challenges are recognizing HLH, determining whether the immune response is aberrant or appropriate, and deciding upon therapy. Patients may present with fever, central nervous system symptoms, cytopenias, or elevated liver enzymes. Recognizing HLH is challenging because its features overlap with numerous systemic disorders, thus requiring a high level of suspicion and timely investigations to confirm the diagnosis and detect the underlying trigger. Once HLH is diagnosed, careful consideration of immunosuppressive therapy's potential benefit versus harm is necessary. Such therapy can sometimes be tailored to the underlying trigger. In the acute setting, the competing pressures of completing a thorough diagnostic process (including evaluation for the presence of lymphoma and infection) and the need for expedited treatment must be balanced. During the management of an HLH patient, continuous vigilance for the presence of as-yet unrecognized disease triggers, monitoring response, and identifying emerging complications is critical. This review will discuss the recognition and management of HLH in the inpatient setting.

Immune Effector Cell-Associated HLH-like Syndrome: A Review of the Literature of an Increasingly Recognized Entity

Since CAR-T cell therapy was initially approved in 2017, its use has become more prevalent and so have its side effects. CAR-T-related HLH, also named immune effector cell-associated HLH-like syndrome (IEC-HS), is a rare but fatal toxicity if not recognized promptly. We conducted a review of the literature in order to understand the prevalence of IEC-HS as well as clarify the evolution of the diagnostic criteria and treatment recommendations. IEC-HS occurrence varies between CAR-T cell products and the type of malignancy treated. Diagnosis can be challenging as there are no standardized diagnostic criteria, and its clinical features can overlap with cytokine release syndrome and active hematological disease. Suggested treatment strategies have been extrapolated from prior experience in HLH and include anakinra, corticosteroids and ruxolitinib. IEC-HS is a potentially fatal toxicity associated with CAR-T cell therapy. Early recognition with reliable diagnostic criteria and prompt implementation of treatment specific to IEC-HS is imperative for improving patient outcomes.

The 2022 EULAR/ACR Points to Consider at the Early Stages of Diagnosis and Management of Suspected Haemophagocytic Lymphohistiocytosis/Macrophage Activation Syndrome (HLH/MAS)

OBJECTIVE

Haemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are life-threatening systemic hyperinflammatory syndromes that can develop in most inflammatory contexts. They can progress rapidly, and early identification and management are critical for preventing organ failure and mortality. This effort aimed to develop evidence-based and consensus-based points to consider to assist clinicians in optimising decision-making in the early stages of diagnosis, treatment and monitoring of HLH/MAS.

METHODS

A multinational, multidisciplinary task force of physician experts, including adult and paediatric rheumatologists, haematologist/oncologists, immunologists, infectious disease specialists, intensivists, allied healthcare professionals and patients/parents, formulated relevant research questions and conducted a systematic literature review (SLR). Delphi methodology, informed by SLR results and questionnaires of experts, was used to generate statements aimed at assisting early decision-making and optimising the initial care of patients with HLH/MAS.

RESULTS

The task force developed 6 overarching statements and 24 specific points to consider relevant to early recognition of HLH/MAS, diagnostic approaches, initial management and monitoring of HLH/MAS. Major themes included the simultaneous need for prompt syndrome recognition, systematic evaluation of underlying contributors, early intervention targeting both hyperinflammation and likely contributors, careful monitoring for progression/complications and expert multidisciplinary assistance.

CONCLUSION

These 2022 EULAR/American College of Rheumatology points to consider provide up-to-date guidance, based on the best available published data and expert opinion. They are meant to help guide the initial evaluation, management and monitoring of patients with HLH/MAS in order to halt disease progression and prevent life-threatening immunopathology.

Implementing a Disease-specific Multidisciplinary Team and Order Set for Hemophagocytic Lymphohistiocytosis in a Pediatric Hospital

OBJECTIVE

To improve outcomes of hemophagocytic lymphohistiocytosis (HLH), prompt recognition and treatment are necessary. A HLH multidisciplinary team was implemented at our institution, and we established an electronic order set to foster uniformity in the diagnostic approach. The goal of this study is to capture the impact of this diagnostic tool.

METHODS

This is a retrospective study analyzing the utilization of a HLH-specific order set since time of implementation in June 2019 through December 2022. The trends in the utilization of the order set by providers were analyzed to evaluate the awareness and effectiveness of this tool.

RESULTS

The order set was utilized 50 times, most commonly by hematology/oncology (50%) and infectious disease (26%). Utilization by providers on newly presenting patients included 4 times in the year 2019, 12 times in 2020, 16 times in 2021, and 18 times in 2022. Utilization was associated with the diagnosis of HLH in 9 patients (18%).

CONCLUSION

Implementation of an HLH-specific order set facilitated a systematic method to approach patients with suspected HLH. The utilization of the order set displayed an upward trend over time, indicating support of this tool among these providers. This tool can increase awareness and early identification of HLH.

The 2022 EULAR/ACR points to consider at the early stages of diagnosis and management of suspected haemophagocytic lymphohistiocytosis/macrophage activation syndrome (HLH/MAS)

OBJECTIVE

Haemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are life-threatening systemic hyperinflammatory syndromes that can develop in most inflammatory contexts. They can progress rapidly, and early identification and management are critical for preventing organ failure and mortality. This effort aimed to develop evidence-based and consensus-based points to consider to assist clinicians in optimising decision-making in the early stages of diagnosis, treatment and monitoring of HLH/MAS.

METHODS

A multinational, multidisciplinary task force of physician experts, including adult and paediatric rheumatologists, haematologist/oncologists, immunologists, infectious disease specialists, intensivists, allied healthcare professionals and patients/parents, formulated relevant research questions and conducted a systematic literature review (SLR). Delphi methodology, informed by SLR results and questionnaires of experts, was used to generate statements aimed at assisting early decision-making and optimising the initial care of patients with HLH/MAS.

RESULTS

The task force developed 6 overarching statements and 24 specific points to consider relevant to early recognition of HLH/MAS, diagnostic approaches, initial management and monitoring of HLH/MAS. Major themes included the simultaneous need for prompt syndrome recognition, systematic evaluation of underlying contributors, early intervention targeting both hyperinflammation and likely contributors, careful monitoring for progression/complications and expert multidisciplinary assistance.

CONCLUSION

These 2022 EULAR/American College of Rheumatology points to consider provide up-to-date guidance, based on the best available published data and expert opinion. They are meant to help guide the initial evaluation, management and monitoring of patients with HLH/MAS in order to halt disease progression and prevent life-threatening immunopathology.

Hemophagocytic lymphohistiocytosis secondary to unrecognized Bartonella henselae infection: a case report

BACKGROUND

Bartonella henselae is a species of intracellular bacteria transmitted to humans through animal bites and scratches contaminated with the feces of arthropod vectors, and are most commonly associated with cat exposure although transmission from other mammals has been reported. Bartonella henselae infection has a spectrum of clinical manifestations and has rarely been reported as cause of hemophagocytic lymphohistiocytosis (HLH) in immunocompromised hosts.

CASE PRESENTATION

We present a report of Bartonella henselae infection progressing to HLH in an immunocompetent patient. The patient initially presented with regional lymphadenopathy but the diagnosis was not suspected as the patient reported no exposure to cats. On further history, he did report a scratch from a dog prior to development of symptoms. The patient was treated with methylprednisolone, intravenous immunoglobulin and anakinra for the HLH and three months of Doxycycline for Bartonella infection, with complete resolution of symptoms.

CONCLUSIONS

Although commonly associated with cat exposure, Bartonella henselae transmission can occur after exposure to other animals and vectors including dogs and clinicians need to maintain an index of suspicion for timely diagnosis. Bartonella henselae is associated with a spectrum of clinical manifestations which can include disseminated infection with severe complications such as hemophagocytic lymphohistiocytosis. Prompt initiation of Bartonella treatment is essential when thought to be the trigger for hemophagocytic lymphohistiocytosis although the optimal treatment regimen is unclear.

Secondary hemophagocytic lymphohistiocytosis in children (Review)

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening condition characterized by hyperinflammation in an uncontrolled and ineffective immune response. Despite great improvement in diagnosis and treatment, it still represents a challenge in clinical management, with poor prognosis in the absence of an aggressive therapeutic approach. The present literature review focuses on secondary HLH at pediatric age, which represents a heterogeneous group in terms of etiology and therapeutic approach. It summarizes the most recent evidence on epidemiology, pathophysiology, diagnosis, treatment and prognosis, and provides a detailed description and comparison of the major subtypes of secondary HLH. Finally, it addresses the open questions with a focus on diagnosis and new treatment insights.

Secondary haemophagocytic lymphohistiocytosis in a patient with new-onset systemic lupus erythematosus: the challenges of timely diagnosis and successful treatment

Haemophagocytic lymphohistiocytosis (HLH) is an immune-mediated disease driven by abnormal macrophage activation and regulatory cell dysfunction. HLH can be primary due to genetic mutations or secondary due to infection, malignancy or autoimmune conditions. We describe a woman in her early 30s who developed HLH while being treated for newly diagnosed systemic lupus erythematosus (SLE) complicated by lupus nephritis as well as concomitant cytomegalovirus (CMV) reactivation from a dormant infection. The trigger for this secondary form of HLH may have been either aggressive SLE and/or CMV reactivation. Despite prompt treatment with immunosuppressive therapies for SLE consisting of high-dose corticosteroids, mycophenolate mofetil, tacrolimus, etoposide for HLH and ganciclovir for CMV infection, the patient developed multiorgan failure and passed away. We demonstrate the difficulty in identifying a specific cause for secondary HLH when multiple conditions are present (SLE and CMV) and the fact that, despite aggressive treatment for both conditions, the mortality for HLH remains high.

Advances in attractive therapeutic approach for macrophage activation syndrome in COVID-19

Nowadays, people have relaxed their vigilance against COVID-19 due to its declining infection numbers and attenuated virulence. However, COVID-19 still needs to be concern due to its emerging variants, the relaxation of restrictions as well as breakthrough infections. During the period of the COVID-19 infection, the imbalanced and hyper-responsive immune system plays a critical role in its pathogenesis. Macrophage Activation Syndrome (MAS) is a fatal complication of immune system disease, which is caused by the excessive activation and proliferation of macrophages and cytotoxic T cells (CTL). COVID-19-related hyperinflammation shares common clinical features with the above MAS symptoms, such as hypercytokinemia, hyperferritinemia, and coagulopathy. In MAS, immune exhaustion or defective anti-viral responses leads to the inadequate cytolytic capacity of CTL which contributes to prolonged interaction between CTL, APCs and macrophages. It is possible that the same process also occurred in COVID-19 patients, and further led to a cytokine storm confined to the lungs. It is associated with the poor prognosis of severe patients such as multiple organ failure and even death. The main difference of cytokine storm is that in COVID-19 pneumonia is mainly the specific damage of the lung, while in MAS is easy to develop into a systemic. The attractive therapeutic approach to prevent MAS in COVID-19 mainly includes antiviral, antibiotics, convalescent plasma (CP) therapy and hemadsorption, extensive immunosuppressive agents, and cytokine-targeted therapies. Here, we discuss the role of the therapeutic approaches mentioned above in the two diseases. And we found that the treatment effect of the same therapeutic approach is different.