Variability in the efficacy of the IL1 receptor antagonist anakinra for treating Erdheim-Chester disease

Erdheim-Chester disease: Comprehensive insights from genetic mutations to clinical manifestations and therapeutic advances

Erdheim-Chester disease (ECD) is an extremely rare non-Langerhans cell disorder that is believed to include both inflammatory and neoplastic characteristics. It is caused due to genetic mutations in proto-oncogenes like BRAF and MEK, while immunological pathways have an essential role in the onset and progression of the disease. Despite its rarity, ECD poses significant diagnostic and therapeutic challenges due to its heterogeneous clinical presentation and limited understanding of its underlying pathophysiology. Multiple organs can be affected, with the most frequent being long bones, central nervous system and retro-orbital abnormalities, pericardial and myocardial infiltration, interstitial lung disease, retroperitoneal fibrosis, and large blood vessel aberrations. Here, in this review, we comprehensively underline the current knowledge of ECD, including its epidemiology, clinical manifestations, genetics, pathophysiology, diagnostic modalities, and treatment options. By synthesizing existing literature and highlighting areas of ongoing research, this review aims to provide clinicians and researchers with a comprehensive understanding of ECD and guide future directions for improved patient care and outcomes.

Recent advances in therapeutic strategies of Erdheim-Chester disease

Erdheim-Chester disease (ECD) is a rare form of non-LCH characterized by excessive accumulation of histiocytes in various tissues, leading to significant morbidity. The estimated prevalence of ECD is low, with fewer than 1000 cases reported globally, yet it presents considerable clinical challenges due to its heterogeneous manifestations, which include bone pain, cardiovascular complications, and neurological symptoms. Traditional treatment approaches, primarily involving corticosteroids and chemotherapy, have limitations, including inconsistent responses and significant side effects. Recent advances in understanding the pathogenesis of ECD, particularly the role of the BRAF V600E mutation, have led to the exploration of novel therapeutic strategies, such as targeted BRAF inhibitors, MEK and mTOR inhibitors, and other immunotherapies, which offer promise in improving patient outcomes. The review further explores clinical manifestations, and radiographic features of Erdheim-Chester disease, and discusses treatment strategies, current clinical studies in the field of ECD. By integrating these aspects, this review aims to provide a thorough understanding of ECD and its evolving treatment landscape, ultimately contributing to improved patient outcomes.

Orbital histiocytosis; From A to Z

PURPOSE

Histiocytosis is one of the most challenging diseases in medical practice. Because of the broad spectrum of clinical manifestations, systemic involvements, unknown etiology, and complex management, different types of histiocytosis are still a big question mark for us. Orbital histiocytosis is characterized by the abnormal proliferation of histiocytes in orbital tissues. It could affect the orbit, eyelid, conjunctiva, and uveal tract. Orbital histiocytosis can cause limited eye movement, proptosis, decreased visual acuity, and epiphora. In this study, we review the novel findings regarding the pathophysiology, diagnosis, and treatment of different types of histiocytosis, focusing on their orbital manifestations.

METHOD

This review was performed based on a search of the PubMed, Scopus, and Embase databases or relevant published papers regarding orbital histiocytosis on October 9th, 2023. No time restriction was proposed, and articles were excluded if they were not referenced in English.

RESULTS

391 articles were screened, most of them being case reports. The pathophysiology of histiocytosis is still unclear. However, different mutations are found to be prevalent in most of the patients. The diagnostic path can be different based on various factors such as age, lesion site, type of histiocytosis, and the stage of the disease. Some modalities, such as corticosteroids and surgery, are used widely for treatment. On the other hand, based on some specific etiological factors for each type, alternative treatments have been proposed.

CONCLUSION

Significant progress has been made in the detection of somatic molecular changes. Many case studies describe various disease patterns influencing the biological perspectives on different types of histiocytosis. It is necessary to continue investigating and clustering data from a broad range of patients with histiocytosis in children and adults to define the best ways to diagnose and treat these patients.

Successful treatment of cutaneous-onset Erdheim-Chester disease with cobimetinib and anakinra

Erdheim–Chester disease is a rare multisystem non-Langerhans cell histiocytosis. We report the case of a patient with BRAF wildtype Erdheim–Chester disease presenting with facial nodular xanthomas and developing systemic involvement 10 years later. The patient was successfully treated with a combination of anakinra and cobimetinib.

Erdheim-Chester disease: A multisystem disease case illustration with rare manifestations and treatment challenges

Erdheim-Chester disease is a rare multisystemic disease. A 50-year-old woman, presented with a recurrent pain and swelling of the left knee. Bone scintigraphy showed increased tracer uptake of peripheral skeleton. The computed tomography showed tissular infiltration in the retroperitoneum, around the vessels. Immunohistochemistry showed CD68 (+) and CD1a (-).

Extensive Aortic Thromboembolism in a Patient With Erdheim-Chester Disease: A Case Report

Background

Erdheim-Chester disease (ECD) is a rare disease that affects multiple systems and is characterized by non-Langerhans cell histiocytosis. Classic clinical signs include long bone infiltration, central nervous system involvement, diabetes insipidus, and sheathing of the entire aorta. However, thrombosis is not recognized as a typical cardiac manifestation of ECD. Here, we report the case of an ECD patient with extensive arterial thrombus formation and embolism in several sections of the aorta.

Case

A 36-year-old woman was admitted due to recurrent fever and left finger cyanosis for 20 days. Laboratory tests revealed that her C-reactive protein and interleukin-6 levels were significantly elevated. Thoracic computed tomographic angiography (CTA) revealed thrombosis from the aortic arch to the left subclavian artery accompanied by severe stenosis of the left subclavian artery. Abdominal CTA revealed splenic infarction due to splenic artery embolism and thrombus formation in multiple abdominal arteries. She underwent emergent arterial thrombectomy. During hospitalization, she complained of polyuria. The desmopressin test and pituitary magnetic resonance imaging findings suggested diabetes insipidus. Furthermore, positron emission tomography-computed tomography and bone emission computed tomography showed long bone impairment, and pathological examination of the bone samples confirmed ECD. Steroids and tocilizumab were selected as the initial therapies; however, thrombosis continued to develop. After replacement of tocilizumab with interferon-α, her condition became stable.

Conclusion

Although extremely rare, fatal thrombosis may be a significant cardiovascular manifestation of ECD.

Histiocytic Neoplasms, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology

Histiocytic neoplasms are rare hematologic disorders accounting for less than 1% of cancers of the soft tissue and lymph nodes. Clinical presentation and prognosis of these disorders can be highly variable, leading to challenges for diagnosis and optimal management of these patients. Treatment often consists of systemic therapy, and recent studies support use of targeted therapies for patients with these disorders. Observation ("watch and wait") may be sufficient for select patients with mild disease. These NCCN Guidelines for Histiocytic Neoplasms include recommendations for diagnosis and treatment of adults with the most common histiocytic disorders: Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease.

Histiocytic disorders

The historic term 'histiocytosis' meaning 'tissue cell' is used as a unifying concept for diseases characterized by pathogenic myeloid cells that share histological features with macrophages or dendritic cells. These cells may arise from the embryonic yolk sac, fetal liver or postnatal bone marrow. Prior classification schemes align disease designation with terminal phenotype: for example, Langerhans cell histiocytosis (LCH) shares CD207+ antigen with physiological epidermal Langerhans cells. LCH, Erdheim-Chester disease (ECD), juvenile xanthogranuloma (JXG) and Rosai-Dorfman disease (RDD) are all characterized by pathological ERK activation driven by activating somatic mutations in MAPK pathway genes. The title of this Primer (Histiocytic disorders) was chosen to differentiate the above diseases from Langerhans cell sarcoma and malignant histiocytosis, which are hyperproliferative lesions typical of cancer. By comparison LCH, ECD, RDD and JXG share some features of malignant cells including activating MAPK pathway mutations, but are not hyperproliferative. 'Inflammatory myeloproliferative neoplasm' may be a more precise nomenclature. By contrast, haemophagocytic lymphohistiocytosis is associated with macrophage activation and extreme inflammation, and represents a syndrome of immune dysregulation. These diseases affect children and adults in varying proportions depending on which of the entities is involved.

Histiocytosis and the nervous system: from diagnosis to targeted therapies

Histiocytoses are heterogeneous hematopoietic diseases characterized by the accumulation of CD68(+) cells with various admixed inflammatory infiltrates. The identification of the pivotal role of the mitogen-activated protein kinase (MAPK) pathway has opened new avenues of research and therapeutic approaches. We review the neurologic manifestations of 3 histiocytic disorders with frequent involvement of the brain and spine: Langerhans cell histiocytosis (LCH), Erdheim-Chester disease (ECD), and Rosai-Dorfman-Destombes disease (RDD). Central nervous system (CNS) manifestations occur in 10%-25% of LCH cases, with both tumorous or neurodegenerative forms. These subtypes differ by clinical and radiological presentation, pathogenesis, and prognosis. Tumorous or degenerative neurologic involvement occurs in 30%-40% of ECD patients and affects the hypothalamic-pituitary axis, meninges, and brain parenchyma. RDD lesions are typically tumorous with meningeal or parenchymal masses with strong contrast enhancement. Unlike LCH and ECD, neurodegenerative lesions or syndromes have not been described with RDD. Familiarity with principles of evaluation and treatment both shared among and distinct to each of these 3 diseases is critical for effective management. Refractory or disabling neurohistiocytic involvement should prompt the consideration for use of targeted kinase inhibitor therapies.

Histiocytosis

Histiocytoses constitute a heterogeneous group of rare disorders, characterised by infiltration of almost any organ by myeloid cells with diverse macrophage or dendritic cell phenotypes. Histiocytoses can start at any age. Diagnosis is based on histology in combination with appropriate clinical and radiological findings. The low incidence and broad spectrum of clinical manifestations often leads to diagnostic delay, especially for adults. In most cases, biopsy specimens infiltrated by histiocytes have somatic mutations in genes activating the MAP kinase cell-signalling pathway. These mutations might also be present in blood cells and haematopoietic progenitors of patients with multisystem disease. A comprehensive range of investigations and molecular typing are essential to accurately predict prognosis, which can vary from spontaneous resolution to life-threatening disseminated disease. Targeted therapies with BRAF or MEK inhibitors have revolutionised salvage treatment. However, the type and duration of treatment are still debated, and the prevention of neurological sequelae remains a crucial issue.

Oncogene-induced maladaptive activation of trained immunity in the pathogenesis and treatment of Erdheim-Chester disease

Trained immunity (TI) is a pro-inflammatory program induced in monocyte/macrophages upon sensing of specific pathogens and characterized by immunometabolic and epigenetic changes enhancing cytokine production. Maladaptive activation of TI (i.e., in the absence of infection) might result in detrimental inflammation and disease development; however, the exact role and extent of inappropriate activation of TI in the pathogenesis of human diseases is undetermined. Here, we reveal oncogene-induced, maladaptive induction of TI in the pathogenesis of a human inflammatory myeloid neoplasm (Erdheim-Chester disease, ECD, characterized by the BRAFV600E oncogenic mutation in monocyte/macrophages and excess cytokine production). Mechanistically, myeloid cells expressing BRAFV600E exhibit all molecular features of TI: activation of the AKT/mTOR signaling axis; increased glycolysis, glutaminolysis, and cholesterol synthesis; epigenetic changes on promoters of genes encoding cytokines; and enhanced cytokine production leading to hyper-inflammatory responses. In ECD patients, effective therapeutic strategies contrast this maladaptive TI phenotype; in addition, pharmacologic inhibition of immunometabolic changes underlying TI (i.e., glycolysis) effectively dampens cytokine production by myeloid cells. This study reveals the deleterious potential of inappropriate activation of TI in the pathogenesis of human inflammatory myeloid neoplasms, and the opportunity for inhibition of TI in conditions characterized by maladaptive myeloid-driven inflammation.

Erdheim-Chester disease: consensus recommendations for evaluation, diagnosis, and treatment in the molecular era

Erdheim-Chester disease (ECD) is a rare histiocytosis that was recently recognized as a neoplastic disorder owing to the discovery of recurrent activating MAPK (RAS-RAF-MEK-ERK) pathway mutations. Typical findings of ECD include central diabetes insipidus, restrictive pericarditis, perinephric fibrosis, and sclerotic bone lesions. The histopathologic diagnosis of ECD is often challenging due to nonspecific inflammatory and fibrotic findings on histopathologic review of tissue specimens. Additionally, the association of ECD with unusual tissue tropism and an insidious onset often results in diagnostic errors and delays. Most patients with ECD require treatment, except for a minority of patients with minimally symptomatic single-organ disease. The first ECD consensus guidelines were published in 2014 on behalf of the physicians and researchers within the Erdheim-Chester Disease Global Alliance. With the recent molecular discoveries and the approval of the first targeted therapy (vemurafenib) for BRAF-V600-mutant ECD, there is a need for updated clinical practice guidelines to optimize the diagnosis and treatment of this disease. This document presents consensus recommendations that resulted from the International Medical Symposia on ECD in 2017 and 2019. Herein, we include the guidelines for the clinical, laboratory, histologic, and radiographic evaluation of ECD patients along with treatment recommendations based on our clinical experience and review of literature in the molecular era.

Long-term follow-up of mTOR inhibition for Erdheim-Chester disease

Two articles this week focus on Erdheim-Chester disease (ECD), a rare histiocytosis that mainly affects adults. Clonal somatic mutations primarily involving proteins in the BRAF and MPAK pathways have established ECD as a myeloid neoplasm, with targeted therapies now available for patients. In the first paper, an international panel presents new consensus recommendations for evaluation and treatment of ECD. In the second paper, Pegoraro and colleagues present long-term outcomes of patients with ECD treated with sirolimus, with responses in patients both with and without BRAF mutations.

Interleukin 1α: a comprehensive review on the role of IL-1α in the pathogenesis and treatment of autoimmune and inflammatory diseases

The interleukin (IL)-1 family member IL-1α is a ubiquitous and pivotal pro-inflammatory cytokine. The IL-1α precursor is constitutively present in nearly all cell types in health, but is released upon necrotic cell death as a bioactive mediator. IL-1α is also expressed by infiltrating myeloid cells within injured tissues. The cytokine binds the IL-1 receptor 1 (IL-1R1), as does IL-1β, and induces the same pro-inflammatory effects. Being a bioactive precursor released upon tissue damage and necrotic cell death, IL-1α is central to the pathogenesis of numerous conditions characterized by organ or tissue inflammation. These include conditions affecting the lung and respiratory tract, dermatoses and inflammatory skin disorders, systemic sclerosis, myocarditis, pericarditis, myocardial infarction, coronary artery disease, inflammatory thrombosis, as well as complex multifactorial conditions such as COVID-19, vasculitis and Kawasaki disease, Behcet's syndrome, Sjogren Syndrome, and cancer. This review illustrates the clinical relevance of IL-1α to the pathogenesis of inflammatory diseases, as well as the rationale for the targeted inhibition of this cytokine for treatment of these conditions. Three biologics are available to reduce the activities of IL-1α; the monoclonal antibody bermekimab, the IL-1 soluble receptor rilonacept, and the IL-1 receptor antagonist anakinra. These advances in mechanistic understanding and therapeutic management make it incumbent on physicians to be aware of IL-1α and of the opportunity for therapeutic inhibition of this cytokine in a broad spectrum of diseases.

Histiocytic disorders: insights into novel biology and implications for therapy of Langerhans cell histiocytosis and Erdheim-Chester disease

Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD) are caused by mutations of the MAPK pathway, most often BRAFV600E, in myeloid dendritic cells that lead to some overlapping and other unique presentations of the two diseases. LCH occurs in both children and adults, but ECD is primarily found in the latter. The challenges in diagnosing these conditions relates to the rarity of the conditions and that they mimic diseases that are more widely understood, such as certain rashes; bone, lung, and renal diseases; and other malignancies. The histopathology of LCH is definitive, but not so for ECD. Treatment with BRAF and MEK inhibitors has become one of the important advances in the care of these patients.

Erdheim-Chester disease

Erdheim-Chester disease (ECD) is characterized by the infiltration of tissues by foamy CD68+CD1a- histiocytes, with 1500 known cases since 1930. Mutations activating the MAPK pathway are found in more than 80% of patients with ECD, mainly the BRAFV600E activating mutation in 57% to 70% of cases, followed by MAP2K1 in close to 20%. The discovery of BRAF mutations and of other MAP kinase pathway alterations, as well as the co-occurrence of ECD with LCH in 15% of patients with ECD, led to the 2016 revision of the classification of histiocytoses in which LCH and ECD belong to the "L" group. Both conditions are considered inflammatory myeloid neoplasms. Ten percent of ECD cases are associated with myeloproliferative neoplasms and/or myelodysplastic syndromes. Some of the most striking signs of ECD are the long bone involvement (80%-95%), as well as the hairy kidney appearance on computed tomography scan (63%), the coated aorta (40%), and the right atrium pseudo-tumoral infiltration (36%). Central nervous system involvement is a strong prognostic factor and independent predictor of death. Interferon-α seems to be the best initial treatment of ECD. Since 2012, more than 200 patients worldwide with multisystem or refractory ECD have benefitted from highly effective therapy with BRAF and MEK inhibitors. Targeted therapies have an overall, robust, and reproducible efficacy in ECD, with no acquired resistance to date, but their use may be best reserved for the most severe manifestations of the disease, as they may be associated with serious adverse effects and as-yet-unknown long-term consequences.

Clinical presentation, imaging and response to interferon-alpha therapy in Erdheim-Chester disease: case-based review

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis associated with BRAFV600E mutations in more than 50% of cases and presenting with 95% with skeletal lesions. However, cutaneous, pulmonary, large vessels and central nervous system involvement can also occur. We report a case of a 25-year-old woman who was admitted in 2018 for exploration of diffuse bone pain and rashes on the face. Her current symptoms had started 14 months earlier and consisted of bone pain, affecting the legs. She had periodic low-grade fever, asthenia and xanthelasma-like papules appeared on face. At admission, physical examination showed bilateral and symmetrical long bone pain, especially in the knees and multiple xanthelasma-like papules around the eyelids, cheeks and chin. Laboratory tests revealed elevated erythrocyte sedimentation rate and C-reactive protein. Magnetic resonance (MR) imaging showed multiple mixed bone lesions with a hyperintensive MR signal on PD FS and hypointense signal on T1of the femur and tibia. Bone scintigraphy indicated bilateral and symmetrical metaphyseal and diaphyseal increased uptake. Abdominal computed tomography (CT) scan showed infiltration of the perirenal fat. Biopsy of the skin revealed histiocytic infiltration, which was CD68-positive and CD100-positive, confirming the diagnosis of ECD. Patient was treated with interferon-α (IFN-α) plus methylprednisolone. After 6 months of treatment her clinical condition partly improved: a reduction of pain on visual analogue scale (VAS) scale, significant decrease of methylprednisolone dose and specific dynamics according to bone MR imaging data, however, no change in symptoms attributed to skin rash was noted. We also provide the literature review results of IFN-α treatment efficacy in Erdheim-Chester disease involving the skin and musculoskeletal system with MR imaging changes.

Erdheim-Chester disease

Erdheim-Chester disease (ECD) is a rare but increasingly recognized multi-system disorder. Its diagnosis and treatment require integration of clinical information, imaging studies, and pathology studies. Of note, ECD can now be defined as a clonal myeloid disorder due to mutations which activate mitogen-activated protein kinase (MAPK) pathways and where an inflammatory milieu is important in the pathogenesis and clinical manifestations of the disease. Biopsy demonstrating characteristic histopathologic features in addition to clinical and radiographic features, most often sclerosing long bone involvement, is required to establish a diagnosis. Detection of somatic MAPK pathway mutations can also assist in the differential diagnosis of ECD and related histiocytic neoplasms. Also, genetic analysis establishing BRAF and RAS mutational status is critical in all ECD patients, as these features will impact therapy with MAPK inhibition. Therapy is recommended at diagnosis in all patients, except for those patients with minimally symptomatic disease. Prospective therapeutic trials are essential to furthering therapeutic progress in ECD.

Neurological manifestations of Erdheim-Chester Disease

Objective

To characterize the spectrum of neurologic involvement in Erdheim–Chester Disease (ECD), a treatable inflammatory neoplasm of histiocytes.

Methods

Sixty‐two patients with ECD were prospectively enrolled in a natural history study that facilitated collection of clinical, imaging, laboratory, neurophysiologic, and pathologic data.

Results

Ninety‐four percent of the patients had neurologic abnormalities on examination or imaging, and 22% had neurologic symptoms as the initial presentation of ECD. The most common neurologic findings were cognitive impairment, peripheral neuropathy, pyramidal tract signs, cranial nerve involvement, and cerebellar ataxia. Imaging revealed atrophy and demyelination along with focal lesions that were located throughout the nervous system, dura, and extra‐axial structures. The BRAF V600E variant correlated with cerebral atrophy. Brain pathology revealed lipid‐laden, phagocytic macrophages (histiocytes) accompanied by demyelination and axonal degeneration.

Interpretation

In patients with ECD, neurologic morbidity is common and contributes significantly to disability. Since neurologic symptoms can be the presenting feature of ECD and, given the mean delay in ECD diagnosis is 4.2 years, it is critical that neurologists consider of ECD and other histiocytosis in patients with inflammatory, infectious, or neoplastic‐appearing white matter. Furthermore, given the broad spectrum of neurologic involvement, neurologists have an important role in a team of specialists treating ECD patients.

Dual BRAF/MEK blockade restores CNS responses in BRAF-mutant Erdheim-Chester disease patients following BRAF inhibitor monotherapy

Background

Erdheim–Chester disease (ECD), a rare inflammatory myeloid neoplasm, is known to be fundamentally reliant on the constitutive activation of the MAPK signaling pathway in the majority of patients. Consequently, inhibition of the V600E-mutant BRAF kinase has proven to be a safe and efficacious long-term therapeutic strategy for BRAF-mutant ECD patients. Nevertheless, in a subset of patients with CNS disease, the efficacy of long-term treatment may diminish, facilitating suboptimal responses or disease progression.

Methods

We retrospectively describe 3 BRAF-mutant ECD patients whose treatment with Vemurafenib was upgraded to Vemurafenib/Cobimetinib due to either disease progression, insufficient response, or unacceptable toxicity. CNS response to therapy was evaluated using magnetic resonance imaging (MRI) and extra-cranial disease was monitored using ¹⁸F-fludeoxyglucose positron emission tomography/computed tomography (PET/CT).

Results

Three patients with a mean age of 52.6 years were treated with Vemurafenib for a mean duration of 26.6 months (range: 6–52). Monotherapies were upgraded to Vemurafenib/Cobimetinib dual therapy. The combination therapy was administered for a mean duration of 21 months (range: 19–23). All patients exhibited clinical and neurological improvement. Regression of lesions on MRI was noted in 2 patients. Both patients characterized by a PET-avid disease responded to the biological treatment regimen with complete metabolic remissions.

Conclusion

Dual inhibition of BRAF and downstream MEK may be a safe and effective therapeutic strategy for BRAF-mutant ECD patients for whom BRAF inhibitor therapy proved insufficient and as such appropriate for the long-term management of CNS disease in ECD.

Erdheim-Chester disease: An in vivo human model of Mϕ activation at the crossroad between chronic inflammation and cancer

Erdheim-Chester disease (ECD) is a rare histiocytosis characterized by infiltration of multiple tissues by CD68⁺ foamy Mϕs (or 'histiocytes'). Clinical manifestations arise from mass-forming lesions or from tissue and systemic inflammation. ECD histiocytes harbor oncogenic mutations along the MAPK-kinase signaling pathway (BRAF^V600E in more than half of the patients), and secrete abundant pro-inflammatory cytokines and chemokines. Based on these features, ECD is considered an inflammatory myeloid neoplasm, and is accordingly managed with targeted kinase inhibitors or immunosuppressive and cytokine-blocking agents. Evidence is emerging that maladaptive metabolic changes, particularly up-regulated glycolysis, represent an additional, mutation-driven feature of ECD histiocytes, which sustains deregulated and protracted pro-inflammatory activation and cytokine production. Besides translational relevance to the management of ECD patients and to the development of new therapeutic approaches, recognition of ECD as a natural human model of chronic, maladaptive Mϕ activation instructs the understanding of Mϕ dysfunction in other chronic inflammatory conditions.

Hypoalphalipoproteinemia and BRAFV600E Mutation Are Major Predictors of Aortic Infiltration in the Erdheim-Chester Disease

Objective- Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis characterized by the infiltration of multiple tissues with lipid-laden histiocytes. Cardiovascular involvement is frequent in ECD and leads to a severe prognosis. The objective of this study was to determine whether an alteration of lipid metabolism participates in the lipid accumulation in histiocytes and the cardiovascular involvement in ECD. Approach and Results- An analysis of plasma lipid levels indicated that male ECD patients carrying the BRAF^V600E (B-Raf proto-oncogene, serine/threonine kinase) mutation exhibited hypoalphalipoproteinemia, as demonstrated by low plasma HDL-C (high-density lipoprotein cholesterol) levels. Capacity of sera from male BRAF^V600E ECD patients to mediate free cholesterol efflux from human macrophages was reduced compared with control individuals. Cardiovascular involvement was detected in 84% of the ECD patients, and we reported that the presence of the BRAF^V600E mutation and hypoalphalipoproteinemia is an independent determinant of aortic infiltration in ECD. Phenotyping of blood CD14⁺ cells, the precursors of histiocytes, enabled the identification of a specific inflammatory signature associated with aortic infiltration which was partially affected by the HDL phenotype. Finally, the treatment with vemurafenib, an inhibitor of the BRAF^V600E mutation, restored the defective sera cholesterol efflux capacity and reduced the aortic infiltration. Conclusions- Our findings indicate that hypoalphalipoproteinemia in male ECD patients carrying the BRAF^V600E mutation favors the formation of lipid-laden histiocytes. In addition, we identified the BRAF status and the HDL phenotype as independent determinants of the aortic involvement in ECD with a potential role of HDL in modulating the infiltration of blood CD14⁺ cells into the aorta.

Systemic Histiocytosis (Langerhans Cell Histiocytosis, Erdheim-Chester Disease, Destombes-Rosai-Dorfman Disease): from Oncogenic Mutations to Inflammatory Disorders

PURPOSE OF REVIEW

Provide an overview of recent progress in decoding the pathogenesis and treatment of systemic histiocytoses.

RECENT FINDINGS

Advances in molecular techniques over the last few years, enabling the identification of several MAPK mutations in lesion histiocytes, have revolutionized our understanding of histiocytosis that led to a revised classification and new treatments. Since the 2010 discovery of the BRAF^V600E mutation in 57% of Langerhans cell histiocytosis (LCH) lesions, several other kinase mutations have been found, mostly in the MAPK pathway, and also in other key signaling pathways, in LCH, Erdheim-Chester Disease (ECD) and, less frequently, Destombes-Rosai-Dorfman disease (RDD). Those revolutionary breakthroughs enhanced our understanding of the pathogenesis of histiocytosis and led to trials with targeted therapies that demonstrated notable efficacy.

Superior efficacy and similar safety of double dose anakinra in Erdheim-Chester disease after single dose treatment

Objectives. In Erdheim-Chester disease (ECD), the empirical single dose (SD, 100 mg/day) anakinra sometimes induces only partial responses. Since SD is usually well tolerated, doubling the dose might improve response while maintaining an acceptable safety profile. Methods. A retrospective analysis was performed of outcomes under double-dose (DD) of anakinra in 4 ECD patients who did not exhibit a complete response (CR) under SD treatment. Bone, retroperitoneal, neurologic/orbital, peritoneal, pericardial, right atrium, and pleural involvements were recorded. CR, partial response (PR), stable disease, progressive disease (PD) and tolerance of DD were assessed. Results. SD treatment was a second or third line treatment in three patients after interferon-therapy failure. Two patients, including one with a BRAF mutation, achieved a CR and one patient with a NRAS mutation achieved a PR with DD treatment. The fourth patient, wild-type for both genes, did not respond to a first DD treatment, but then achieved CR under SD associated with a reduced dose of vemurafenib (960 mg/d). Bone and retroperitoneal lesions partially improved on imaging with SD in all patients, but were further improved under DD with two patients achieving CR. With SD treatment, two patients with right atrial masses showed sustained CR. Under DD treatment, two patients with massive serositis refractory to SD, showed PR. Conclusion. DD improved the response to anakinra and lead to two CRs and a PR in three out of four ECD patients, with minor and comparable side-effects to those of SD, while failures were essentially related to massive serositis.

Interleukin-1 Blockade: An Update on Emerging Indications

Interleukin (IL)-1 is a pro-inflammatory cytokine that induces local and systemic inflammation aimed to eliminate microorganisms and tissue damage. However, an increasing number of clinical conditions have been identified in which IL-1 production is considered inappropriate and IL-1 is part of the disease etiology. In autoinflammatory diseases, gout, Schnitzler's syndrome, and adult-onset Still's disease, high levels of inappropriate IL-1 production have been shown to be a key process in the etiology of the disease. In these conditions, blocking IL-1 has proven very effective in clinical studies. In other diseases, IL-1 has shown to be present in disease process but is not the central driving force of inflammation. In these conditions, including type 1 and 2 diabetes mellitus, acute coronary syndrome, amyotrophic lateral sclerosis, and several neoplastic diseases, the benefits of IL-1 blockade are minimal or absent.

Erdheim-Chester Disease Involving Lymph Nodes and Liver Clinically Mimicking Lymphoma: A Case Report

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis and multisystem disease. First described in 1930, there are no more than 750 cases reported. The etiology remains unknown, but a majority of cases of ECD and Langerhans cell histiocytosis were found to have clonal mutations involving genes of the mitogen-activated protein kinase pathway. We recently encountered a 53-year-old male patient with extensive ECD involving the systemic lymph nodes, pleura, liver, and long bones clinically mimicking malignant lymphoma. Biopsies were performed at multiple sites, including a pleural mass, an external iliac lymph node, bone marrow, and the liver. Based on histopathological and immunohistochemical findings of positivity for CD68 and negativity for CD1a and S-100, the patient was diagnosed with ECD. Interferon-α was administered as the first-line treatment, but the patient rapidly progressed to hepatic failure after 2 months of treatment. We report this rare case of ECD clinically mimicking malignant lymphoma and diagnosed by careful pathological review.

An unusual case of interstitial lung disease in a patient with cardiopulmonary syndrome as the initial presentation of Erdheim-Chester disease

Erdheim-Chester disease (ECD) is a very rare disorder with only approximately 600 cases reported in the literature. ECD has been recently reclassified as a histiocytic dendritic cell neoplasm. The clinical spectrum ranges from asymptomatic tissue accumulation of histiocytes to invasive tissue infiltration, which can cause fulminant multisystem failure. It typically presents with bone pain and constitutional symptoms. Extraosseous manifestations are not uncommon. ECD-associated interstitial lung disease has been described in 20%-35% of patients. Diagnosis is primarily by tissue biopsy and immunohistochemistry showing xanthogranulomas composed of foamy histiocytes that stain positive for CD68, CD14 and CD163 and negative for CD1á and langerin. We report a case of ECD in a young man with cardiopulmonary involvement who presented with haemoptysis and dyspnoea.

Targeting the interleukin-1 pathway in patients with hematological disorders

Interleukin-1α (IL-1α) and IL-1β are potent inflammatory cytokines that activate local and systemic inflammatory processes and are involved in protective immune responses against infections. However, their dysregulated production and signaling can aggravate tissue damage during infection, inflammatory diseases, and chemotherapy-induced intestinal mucositis. Additionally, cytokines of the IL-1 family play an important role in homeostatic as well as "emergency" hematopoiesis and are involved in the pathogenesis of several myeloid and lymphoid hematological malignancies. In the pathogenesis of intestinal mucositis and graft-versus-host disease (GVHD), these cytokines are considered pivotal during the initiation as well as propagation phase, and insights from animal studies suggest that targeting the IL-1 pathway can significantly ameliorate mucositis and GVHD. Moreover, IL-1α and IL-1β might prove to be valuable targets for both prevention and treatment of cancer and cancer therapy-related complications, and the first clinical studies have already been performed in the setting of hematological malignancies. In this review, we will discuss the role of cytokines of the IL-1 family in hematological malignancies, chemotherapy-induced intestinal mucositis, and GVHD, and speculate on possibilities of therapeutically targeting the IL-1 pathway in hematological patients.

Adult Xanthogranulomatous Disease of the Orbit: Clinical Presentations, Evaluation, and Management

Adult xanthogranulomatous disease of the orbit refers to a heterogeneous group of clinical syndromes with differing degrees of systemic involvement and distinct prognoses. The different syndromes all present clinically with progressively enlarging, yellowish lesions of the orbit. Histologically, the lesions are characterized by an inflammatory infiltrate of foam cells and Touton-type multinucleated giant cells. The xanthomatized histiocytes are CD68⁺, S100^-, and CD1a^-. There are 4 clinical forms of xanthogranulomatous disease of the orbit: adult xanthogranulomatous disease of the orbit, adult onset asthma and periocular xanthogranuloma, necrobiotic xanthogranuloma, and Erdheim-Chester disease. The treatment of local lesions are treated with systemic corticosteroids and other immunosuppressors. Vemurafenib, tocilizumab, and sirolimus have shown promising results in systemic disease.