The interferon-gamma pathway is selectively up-regulated in the liver of patients with secondary hemophagocytic lymphohistiocytosis

Liver Dysfunction in Adult Hemophagocytic Lymphohistiocytosis: A Narrative Review

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening condition that has been increasingly recognized in adults and is characterized by a hyperinflammatory state due to immune dysregulation. Its nonspecific presentation, the lack of clinician familiarity given its rarity, and shared clinical features with sepsis and other syndromes can lead to a delay in diagnosis and a poor prognosis. Significant liver function abnormalities as the initial manifestation of HLH are uncommon and can range from mild elevation of aminotransferases to fulminant hepatic failure with high mortality rates. The authors encountered a case of adult HLH mimicking acute viral hepatitis in which a markedly elevated ferritin level led to a prompt diagnosis, early initiation of treatment, and a successful outcome. Clinicians, including gastroenterologists and hepatologists, are often called upon to evaluate patients with abnormal liver tests and may lack experience in the early diagnosis and management of liver dysfunction in the context of HLH. Thus, we expand our reporting to a narrative review of literature which explores the pathogenesis of HLH, challenges associated with its diagnosis, previous reports of liver disease associated with the syndrome, recommended treatments for the familial and adult variations including the role of liver transplantation, and the outcomes of these treatments.

The 4th NextGen therapies for SJIA and MAS: part 2 phenotypes of refractory SJIA and the landscape for clinical trials in refractory SJIA

Although the introduction of the IL-1 and IL-6 inhibiting biologics in 2012 has revolutionized the treatment and markedly improved outcomes for many patients with SJIA, about 20% of these patients continue to have active disease, have markedly decreased quality of life and high disease activity as well as treatment-related morbidity and mortality. There is a clear need to define these disease states, and then use these definitions as the basis for further studies into the prevalence, clinical features, and pathophysiologic mechanisms. While such patients are most likely to benefit from novel therapies, they are very difficult to enroll in the ongoing clinical trials given the unique features of their disease and large numbers of background medications. The discussions at the NextGen 2022 conference focused on strategies to overcome these obstacles and accelerate studies in refractory SJIA.

Type 1 Interferon-Stimulated Gene Expression and Disease Activity in Pediatric Rheumatic Diseases: No Composite Scores Needed?

OBJECTIVE

Rheumatic diseases are characterized by different patterns of immune overactivation. This study investigated the correlation of whole blood type 1 interferon (IFN) stimulated gene (ISG), IL18, and CXCL9 expression with clinical disease activity in pediatric rheumatic diseases and assessed the required number of ISGs to be included in a composite type 1 IFN score.

METHODS

Whole blood-derived RNA and clinical data were collected from 171 mostly pediatric patients with connective tissue diseases (CTDs), systemic autoinflammatory diseases (SAIDs), monogenic interferonopathies (IFNPs) and other inflammatory diseases, and from 38 controls. The expression of six previously established ISGs, IL18, and CXCL9 was assessed by real-time polymerase chain reaction (471 samples). Individual and composite gene expression was assessed, and correlation and threshold analyses were performed.

RESULTS

Correlation between ISG expression and clinical disease activity was strongest in CTD, especially in juvenile dermatomyositis (JDM) and IFNP, and modest in patients with SAID. Threshold ISG expression levels for the detection of at least mild clinical disease activity were substantially higher in patients with systemic lupus erythematosus compared with JDM. The correlation of expression levels of limited sets of ISGs and even individual ISGs with clinical disease activity were not inferior to a composite score of six ISGs.

CONCLUSION

In a real-world cohort, individual ISG expression levels robustly reflected clinical disease activity in CTD and IFNP, especially in JDM, which would simplify such analyses in clinical routine and be more cost-effective. Threshold levels varied across diseases, potentially reflecting different mechanisms of type 1 IFN overactivation.

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.

The Liver in Hemophagocytic Lymphohistiocytosis: Not an Innocent Bystander

Hemophagocytic lymphohistiocytosis (HLH) is a rare multisystemic hyperinflammatory disease commonly associated with hepatic dysfunction. Liver injury is mediated by unchecked antigen presentation, hypercytokinemia, dysregulated cytotoxicity by natural killer and CD8 T cells, and disruption of intrinsic hepatic metabolic pathways. Over the past decade, there have been significant advances in diagnostics and expansion in therapeutic armamentarium for this disorder allowing for improved morbidity and mortality. This review discusses the clinical manifestations and pathogenesis of HLH hepatitis in both familial and secondary forms. It will review growing evidence that the intrinsic hepatic response to hypercytokinemia in HLH perpetuates disease progression and the novel therapeutic approaches for patients with HLH-hepatitis/liver failure.

CXCL9 inhibition does not ameliorate disease in murine models of both primary and secondary hemophagocytic lymphohistiocytosis

Hemophagocytic Lymphohistiocytosis (HLH) is a group of disorders culminating in systemic inflammation and multi-organ failure with high incidence of hepatic dysfunction. Overproduction of IFN-γ is the main immunopathological driver in this disorder. Monokine induced by IFN-γ (CXCL9) serves as a biomarker for disease activity and response to treatment in this disorder. However, very little is understood about the actual functional role of CXCL9 in pathogenesis in HLH. In the current study, we sought to determine the role of CXCL9 in pathogenesis in murine models of both Familial HLH (prf1^-/-) and Toll Like Receptor (TLR) 9 repeated stimulation induced Macrophage Activation Syndrome (MAS), a form of secondary HLH. FHL and MAS were induced in both CXCL9 genetically deficient mice (cxcl9^-/-) and controls as well as using AMG487, a pharmacological antagonist of the CXCL9 receptor, CXCR3. Results showed that CXCL9 genetic deficiency did not improve disease parameters or hepatitis in both models. Consistent with genetic ablation of CXCL9, inhibition of its receptor, CXCR3, by AMG487 did not show any significant effects in the FHL model. Taken together, inhibition of CXCL9-CXCR3 interaction does not ameliorate HLH physiology in general, or hepatitis as a classical target organ of disease.

Familial hemophagocytic lymphohistiocytosis hepatitis is mediated by IFN-γ in a predominantly hepatic-intrinsic manner

Interferon gamma (IFN-γ) is the main cytokine driving organ dysfunction in Familial Hemophagocytic Lymphohistiocytosis (FHL). Blockade of IFN-γ pathway ameliorates FHL hepatitis, both in animal models and in humans with FHL. Hepatocytes are known to express IFN-γ receptor (IFN-γ-R). However, whether IFN-γ induced hepatitis in FHL is a lymphocyte or liver intrinsic response to the cytokine has yet to be elucidated. Using a IFNgR-/- bone marrow chimeric model, this study showed that non-hematopoietic IFN-γ response is critical for development of FHL hepatitis in LCMV-infected Prf1-/- mice. Lack of hepatic IFN-γ responsiveness results in reduced hepatitis as measured by hepatomegaly, alanine aminotransferase (ALT) levels and abrogated histologic endothelial inflammation. In addition, IFN-γ non-hematopoietic response was critical in activation of lymphocytes by soluble interleukin 2 receptor (sIL-2r) and recruitment of CD8+ effector T lymphocytes (CD8+ CD44hi CD62Llo) (Teff) and inflammatory monocytes. Lastly, non-hematopoietic IFN-γ response results in increased hepatic transcription of type 1 immune response and oxidative stress response pathways, while decreasing transcription of genes involved in extracellular matrix (ECM) production. In summary, these findings demonstrate that there is a hepatic transcriptional response to IFN-γ, likely critical in the pathogenesis of FHL hepatitis and hepatic specific responses could be a therapeutic target in this disorder.

Targeting interferon-γ in hyperinflammation: opportunities and challenges

Interferon-γ (IFNγ) is a pleiotropic cytokine with multiple effects on the inflammatory response and on innate and adaptive immunity. Overproduction of IFNγ underlies several, potentially fatal, hyperinflammatory or immune-mediated diseases. Several data from animal models and/or from translational research in patients point to a role of IFNγ in hyperinflammatory diseases, such as primary haemophagocytic lymphohistiocytosis, various forms of secondary haemophagocytic lymphohistiocytosis, including macrophage activation syndrome, and cytokine release syndrome, all of which are often managed by rheumatologists or in consultation with rheumatologists. Given the effects of IFNγ on B cells and T follicular helper cells, a role for IFNγ in systemic lupus erythematosus pathogenesis is emerging. To improve our understanding of the role of IFNγ in human disease, IFNγ-related biomarkers that are relevant for the management of hyperinflammatory diseases are progressively being identified and studied, especially because circulating levels of IFNγ do not always reflect its overproduction in tissue. These biomarkers include STAT1 (specifically the phosphorylated form), neopterin and the chemokine CXCL9. IFNγ-neutralizing agents have shown efficacy in the treatment of primary haemophagocytic lymphohistiocytosis in clinical trials and initial promising results have been obtained in various forms of secondary haemophagocytic lymphohistiocytosis, including macrophage activation syndrome. In clinical practice, there is a growing body of evidence supporting the usefulness of circulating CXCL9 levels as a biomarker reflecting IFNγ production.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Non-proliferative and Proliferative Lesions of the Non-human Primate (M. fascicularis)

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in most tissues and organs from the nonhuman primate used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

High Mortality of HLH in ICU Regardless Etiology or Treatment

Background: Adult hemophagocytic lymphohistiocytosis (HLH) is highly lethal in the ICU. The diagnostic and therapeutic emergency that HLH represents is compounded by its unknown pathophysiological mechanisms. Here, we report on a large cohort of adult HLH in the ICU (ICU-HLH). We analyzed prognostic factors associated with mortality to define the diagnostic and therapeutic challenges in this specific population. Methods: This retrospective study included adult patients diagnosed with HLH in four ICUs in Marseille, France between 2010 and 2020. Patients who fulfilled the HLH-2004 criteria (≥ 4/8) and/or had an HScore ≥ 169 were diagnosed with HLH. HLH was categorized into four groups according to etiology: sepsis-associated HLH, intracellular infection-associated HLH, malignancy-associated HLH, and idiopathic HLH. Results: Two hundred and sixty patients were included: 121 sepsis-associated HLH (47%), 84 intracellular infection-associated HLH (32%), 28 malignancy-associated HLH (11%), and 27 idiopathic HLH (10%). The ICU mortality rate reached 57% (n = 147/260) without a statistical difference between etiological groups. Independent factors associated with mortality in multivariate analysis included age (OR (5 years) = 1.31 [1.16-1.48], p < 0.0001), SOFA score at ICU admission (OR = 1.37 [1.21-1.56], p < 0.0001), degradation of the SOFA score between ICU arrival and HLH diagnosis (Delta SOFA) (OR = 1.47 [1.28-1.70], p < 0.0001), the presence of bone-marrow hemophagocytosis (OR = 5.27 [1.11-24.97], p = 0.04), highly severe anemia (OR = 1.44 [1.09-1.91], p = 0.01), and hypofibrinogenemia (OR = 1.21 [1.04-1.41], p = 0.02). Conclusions: In this large retrospective cohort study of critically ill patients, ICU-HLH in adults was associated with a 57% mortality rate, regardless of HLH etiology or specific treatment. Factors independently associated with prognosis included age, presence of hemophagocytosis in bone-marrow aspirates, organ failure at admission, and worsening organ failure during the ICU stay. Whether a rapid diagnosis and the efficacy of specific therapy improve outcome is yet to be prospectively investigated.

Characterization of HLH-Like Manifestations as a CRS Variant in Patients Receiving CD22 CAR T-Cells

CAR T-cell toxicities resembling hemophagocytic lymphohistiocytosis (HLH) occur in a subset of patients with cytokine release syndrome (CRS). As a variant of conventional CRS, a comprehensive characterization of CAR T-cell associated HLH (carHLH) and investigations into associated risk factors are lacking. In the context of 59 patients infused with CD22 CAR T-cells where a substantial proportion developed carHLH, we comprehensively describe the manifestations and timing of carHLH as a CRS variant and explore factors associated with this clinical profile. Amongst 52 subjects with CRS, 21 (40.4%) developed carHLH. Clinical features of carHLH included hyperferritinemia, hypertriglyceridemia, hypofibrinogenemia, coagulopathy, hepatic transaminitis, hyperbilirubinemia, severe neutropenia, elevated lactate dehydrogenase and occasionally hemophagocytosis. Development of carHLH was associated with pre-infusion NK-cell lymphopenia and higher bone marrow T/NK-cell ratio, which was further amplified with CAR T-cell expansion. Following CRS, more robust CAR T-cell and CD8 T-cell expansion in concert with pronounced NK-cell lymphopenia amplified pre-infusion differences in those with carHLH without evidence for defects in NK-cell mediated cytotoxicity. CarHLH was further characterized by persistent elevation of HLH-associated inflammatory cytokines, which contrasted with declining levels in those without carHLH. In the setting of CAR T-cell mediated expansion, clinical manifestations and immunophenotypic profiling in those with carHLH overlap with features of secondary HLH, prompting consideration of an alternative framework for identification and management of this toxicity profile to optimize outcomes following CAR T-cell infusion.

IFN-γ signature in the plasma proteome distinguishes pediatric hemophagocytic lymphohistiocytosis from sepsis and SIRS

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome characterized by pathologic immune activation in which prompt recognition and initiation of immune suppression is essential for survival. Children with HLH have many overlapping clinical features with critically ill children with sepsis and systemic inflammatory response syndrome (SIRS) in whom alternative therapies are indicated. To determine whether plasma biomarkers could differentiate HLH from other inflammatory conditions and to better define a core inflammatory signature of HLH, concentrations of inflammatory plasma proteins were compared in 40 patients with HLH to 47 pediatric patients with severe sepsis or SIRS. Fifteen of 135 analytes were significantly different in HLH plasma compared with SIRS/sepsis, including increased interferon-γ (IFN-γ)-regulated chemokines CXCL9, CXCL10, and CXCL11. Furthermore, a 2-analyte plasma protein classifier including CXCL9 and interleukin-6 was able to differentiate HLH from SIRS/sepsis. Gene expression in CD8+ T cells and activated monocytes from blood were also enriched for IFN-γ pathway signatures in peripheral blood cells from patients with HLH compared with SIRS/sepsis. This study identifies differential expression of inflammatory proteins as a diagnostic strategy to identify critically ill children with HLH, and comprehensive unbiased analysis of inflammatory plasma proteins and global gene expression demonstrates that IFN-γ signaling is uniquely elevated in HLH. In addition to demonstrating the ability of diagnostic criteria for HLH and sepsis or SIRS to identify groups with distinct inflammatory patterns, results from this study support the potential for prospective evaluation of inflammatory biomarkers to aid in diagnosis of and optimizing therapeutic strategies for children with distinctive hyperinflammatory syndromes.

The cytokine storms of COVID-19, H1N1 influenza, CRS and MAS compared. Can one sized treatment fit all?

An analysis of published data appertaining to the cytokine storms of COVID-19, H1N1 influenza, cytokine release syndrome (CRS), and macrophage activation syndrome (MAS) reveals many common immunological and biochemical abnormalities. These include evidence of a hyperactive coagulation system with elevated D-dimer and ferritin levels, disseminated intravascular coagulopathy (DIC) and microthrombi coupled with an activated and highly permeable vascular endothelium. Common immune abnormalities include progressive hypercytokinemia with elevated levels of TNF-α, interleukin (IL)-6, and IL-1β, proinflammatory chemokines, activated macrophages and increased levels of nuclear factor kappa beta (NFκB). Inflammasome activation and release of damage associated molecular patterns (DAMPs) is common to COVID-19, H1N1, and MAS but does not appear to be a feature of CRS. Elevated levels of IL-18 are detected in patients with COVID-19 and MAS but have not been reported in patients with H1N1 influenza and CRS. Elevated interferon-γ is common to H1N1, MAS, and CRS but levels of this molecule appear to be depressed in patients with COVID-19. CD4+ T, CD8+ and NK lymphocytes are involved in the pathophysiology of CRS, MAS, and possibly H1N1 but are reduced in number and dysfunctional in COVID-19. Additional elements underpinning the pathophysiology of cytokine storms include Inflammasome activity and DAMPs. Treatment with anakinra may theoretically offer an avenue to positively manipulate the range of biochemical and immune abnormalities reported in COVID-19 and thought to underpin the pathophysiology of cytokine storms beyond those manipulated via the use of, canakinumab, Jak inhibitors or tocilizumab. Thus, despite the relative success of tocilizumab in reducing mortality in COVID-19 patients already on dexamethasone and promising results with Baricitinib, the combination of anakinra in combination with dexamethasone offers the theoretical prospect of further improvements in patient survival. However, there is currently an absence of trial of evidence in favour or contravening this proposition. Accordingly, a large well powered blinded prospective randomised controlled trial (RCT) to test this hypothesis is recommended.

Monocytes From Patients With Macrophage Activation Syndrome and Secondary Hemophagocytic Lymphohistiocytosis Are Hyperresponsive to Interferon Gamma

Objective

To investigate the activation of the IFNγ signaling pathway in monocytes of patients with secondary hemophagocytic lymphohistiocytosis (sHLH)/macrophage activation syndrome (MAS) and to evaluate whether levels of phosphorylated STAT1 represent a biomarker for the identification of patients at early stages of the disease.

Methods

Fresh whole blood samples from pediatric patients with active sHLH/MAS, not receiving (n=10) and receiving glucocorticoids (n=14) at time of sampling, were prospectively collected. As disease control groups, patients with active systemic juvenile idiopathic arthritis (sJIA) without MAS, patients with sHLH/MAS in remission and patients with other rheumatic diseases were also sampled. Whole blood cells were left unstimulated or stimulated with increasing concentrations of IFNγ for 10 minutes and the intracellular Tyrosine (701)-phosphorylated STAT1 (pSTAT1) levels were evaluated in monocytes by flow cytometry.

Results

Monocytes from untreated sHLH/MAS patients showed significantly higher basal levels of pSTAT1 compared to those observed in monocytes from glucocorticoid-treated sHLH/MAS patients and from all the other disease controls. In addition, a significant increase in responsiveness to IFNγ, as assessed by increased levels of pSTAT1 following ex vivo stimulation, was observed in monocytes from untreated sHLH/MAS patients. pSTAT1 levels in monocytes distinguished patients with sHLH/MAS not treated with glucocorticoids from patients with active sJIA or with other rheumatic diseases [AUC, 0.93; 95% confidence interval 0.85-1.00, p<0.001]. Statistically significant correlations between IFNG mRNA levels in whole blood cells, circulating IFNγ levels and pSTAT1 levels in sHLH/MAS monocytes were found.

Conclusion

Our data demonstrating higher basal levels of pSTAT1 as well as a hyperreactivity to IFNγ stimulation in monocytes from patients with sHLH/MAS point to perturbations in the activation of downstream IFNγ signaling pathway as a contributor to the hyperinflammation occurring in these patients. Finally, the observation that glucocorticoids affect pSTAT1 levels in vivo, makes it difficult to consider the measurement of pSTAT1 levels as a biomarker to identify patients at early stages of sHLH/MAS in clinical practice.

Lung involvement in monogenic interferonopathies

Monogenic type I interferonopathies are inherited heterogeneous disorders characterised by early onset of systemic and organ specific inflammation, associated with constitutive activation of type I interferons (IFNs). In the last few years, several clinical reports identified the lung as one of the key target organs of IFN-mediated inflammation. The major pulmonary patterns described comprise children's interstitial lung diseases (including diffuse alveolar haemorrhages) and pulmonary arterial hypertension but diagnosis may be challenging. Respiratory symptoms may be either mild or absent at disease onset and variably associated with systemic or organ specific inflammation. In addition, associated extrapulmonary clinical features may precede lung function impairment by years, and patients may display severe/endstage lung involvement, although this may be clinically hidden during the long-term disease course. Conversely, a few cases of atypical severe lung involvement at onset have been reported without clinically manifested extrapulmonary signs. Hence, a multidisciplinary approach involving pulmonologists, paediatricians and rheumatologists should always be considered when a monogenic interferonopathy is suspected. Pulmonologists should also be aware of the main pattern of presentation to allow prompt diagnosis and a targeted therapeutic strategy. In this regard, promising therapeutic strategies rely on Janus kinase-1/2 (JAK-1/2) inhibitors blocking the type I IFN-mediated intracellular cascade.

Progressive severe lung impairment may occur clinically hidden during monogenic interferonopathies. Pulmonologists should be aware of the main patterns of presentation in order to allow prompt diagnosis and initiate targeted therapeutic strategy.https://bit.ly/2UeAeLn

The Prognosis Role of AST/ALT (De Ritis) Ratio in Patients with Adult Secondary Hemophagocytic Lymphohistiocytosis

PURPOSE

Secondary hemophagocytic lymphohistiocytosis (sHLH) accompanied by liver involvement, characterized by hepatomegaly and increased liver enzymes, is usually associated with elevated mortality. However, the magnitude of these associations remains unknown. Our objective was to assess the associations of the aspartate transaminase/alanine transaminase (AST/ALT, De Ritis) ratio with overall survival among adult patients with sHLH.

METHODS

A retrospective analysis was performed on 289 patients aged 18-86 years with complete serum transaminase data at diagnosis of sHLH. Multivariate Cox regression analyses and restricted cubic splines were conducted to address the association between the De Ritis ratio and the risk of mortality.

RESULTS

The median De Ritis ratio for the entire study population was 1.34 (IQR: 0.84-2.29). After a median follow-up time of 60 (range 17-227.5) days, 205 deaths occurred. After fully adjusting for hepatomegaly, albumin, fibrinogen, EBV, ferritin, etiologies, and treatment strategies, the adjusted hazard ratios (HRs) with corresponding confidence intervals (CIs) of mortality for the 2 st tertile and 3 st tertile were 1.2 (0.8-1.7) and 1.6 (1.1-2.2), respectively (P < 0.01 for trends). Restricted cubic spline confirmed a linear association between the log2-transformed De Ritis ratio and the risk of mortality. Moreover, this trend persisted in subgroups with MHLH, hyperferrinaemia, sCD25 ≤ 20,000 ng/L, patients without EBV infection, and those received treatment.

CONCLUSIONS

The De Ritis ratio is a strong and independent predictor for overall survival in patients with sHLH. As a readily available biomarker in routine clinical practice, it is used to identify patients with sHLH with inferior overall survival.

Proceedings from the 2nd Next Gen Therapies for Systemic Juvenile Idiopathic Arthritis and Macrophage Activation Syndrome symposium held on October 3-4, 2019

For reasons poorly understood, and despite the availability of biological medications blocking IL-1 and IL-6 that have markedly improved overall disease control, children with Systemic Juvenile Idiopathic Arthritis (SJIA) are now increasingly diagnosed with life-threatening chronic complications, including hepatitis and lung disease (SJIA-LD). On October 3-4, 2019, a two-day meeting, NextGen Therapies for Systemic Juvenile Idiopathic Arthritis (SJIA) & macrophage activation syndrome (MAS) organized by the Systemic JIA Foundation ( www.systemicjia.org/ ) in Washington, DC brought together scientists, clinicians, parents and FDA representatives with the objectives (1) to integrate clinical and research findings in MAS and SJIA-LD, and (2) to develop a shared understanding of this seemingly new pulmonary complication of SJIA. The current manuscript summarizes discussions and conclusions of the meeting.