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Abstract Background Erdheim-Chester disease (ECD) is a very rare histiocytic/dendritic cell neoplasm driven by mutations in genes of the MAPK pathway, such as BRAFV600E. Its clinical presentation is highly heterogeneous, and data on its natural history and prognosis in large cohorts are limited. Here, we investigated the clinical features and outcomes of a very large international cohort of patients with ECD. Methods We included patients diagnosed with ECD between 1990 and 2024, followed at 13 referral centers in Europe and the Americas, who had available clinical and follow-up data (with a minimal follow-up duration of 6 months). We analyzed the clinical presentation, treatment, and outcomes, and sought to identify predictors of survival. The study was conceived and conducted within the ECD Global Alliance network. Results A total of 1044 patients with ECD were included. The median age at diagnosis was 57 years (IQR 46-66), and the male-to-female ratio was 2.2. The median age at the first ECD manifestation was 55 years (IQR 43-65). Bone pain (20%), kidney and urinary manifestations (18%), and diabetes insipidus (11%) were the most frequently reported initial features. The median number of involved sites was 4 (IQR 3-6), most frequently including the long bones (n=768, 74%), the retroperitoneum, (n=605, 58%), the periaortic space (n=449, 43%), the CNS (n=368, 35%), the facial/orbit area (n=347, 33%), and the heart (n=334, 32%). Among 955 tested patients, 572 (60%) harbored the BRAFV600E mutation, and 86 (9%) a MAP2K1 mutation. Clinical and/or pathology overlap with Langerhans cell histiocytosis and Rosai-Dorfman-Destombes disease was observed in 115 (11%) and 42 (4%) patients, respectively. Clonal hematopoiesis was identified in 217 of 556 tested patients (39%), and a history of second cancer was reported in 272 patients (26%), including both solid (14%) and hematologic (12%) neoplasms. First-line treatment mostly included interferon-alpha (n=342, 33%) and BRAFi/MEKi (n=314, 30%), while second- and third-line treatments mostly consisted of BRAFi/MEKi (55% and 63%, respectively). After a median follow-up of 51 months (IQR 20-89), 222 (21%) patients died; causes of death were related to ECD in almost half of the patients (n=101). A multivariate Cox regression model identified the following factors as significantly associated with increased mortality: older age (HR 1.058, 95%CI 1.033-1.083; p<0.001), pseudo-neurodegenerative lesions (HR 2.280, 95%CI 1.337-3.891; p=0.022), elevated CRP at diagnosis (HR 2.574, 95%CI 1.024-6.467; p=0.044), and second hematologic cancer (HR 2.639, 95%CI 1.602-4.348; p<0.001). Conclusions Despite advances in treatments over the last decade, ECD remains associated with substantial mortality. Age, neurodegenerative lesions, elevated CRP levels, and the presence of a second hematologic cancer are the main predictors of poor survival.

ObjectiveErdheim‐Chester disease (ECD) is rare histiocytosis with a wide range of clinical manifestations. Somatic mutations are key to the pathogenesis of the disease; however, the relationship between germline genetic variants and ECD has not been examined so far. The present study aims to explore the inherited genetic component of ECD by performing the first genome‐wide association study.MethodsAfter quality controls, a cohort of 255 patients with ECD and 7,471 healthy donors was included in this study. Afterward, a logistic regression followed by in silico functional annotation was performed.ResultsA signal at the 18q12.3 genomic region was identified as a new susceptibility locus for ECD (P = 2.75 × 10−11; Odds Ratio = 2.09). This association was annotated to the SETBP1 gene, which is involved in clonal haematopoiesis. Functional annotation of this region and of the identified suggestive signals revealed additional genes that could be potentially involved in the pathogenesis of the disease.ConclusionOverall, this work demonstrates that germline genetic variants can impact on the development of ECD and suggests new pathways with a potential pathogenic role.image

ABSTRACT Background Uncertainties exist about the use of mycophenolate mofetil (MMF) in anti-neutrophil cytoplasmatic antibody (ANCA)-associated vasculitis (AAV), particularly for remission maintenance. Methods Systematic review and meta-analysis of phase II and III trials assessing the use of MMF in AAV, granulomatosis with polyangiitis and microscopic polyangiitis (MPA). A comprehensive search of several databases (Medline, EMBASE, Cochrane, Web of Science, Scopus) from inception to 5 May 2020 has been conducted. Trial data were extracted to estimate odds ratios (ORs) and estimates (ES) for MMF efficacy (remission-induction and maintenance). Severe adverse effects (SAEs) were collected. Results From 565 articles captured, 10 met the predefined criteria, 5 phase II and 5 III trials; 4 assessed remission-induction, 3 remission maintenance and 3 both. The pooled OR for remission-induction at 6 months was 1.06 (95% confidence interval 0.74, 1.52), with no significant difference by subgroup meta-analysis of trials stratified by different study-level features (i.e. kidney disease, MPA, myeloperoxidase-ANCA positivity, newly diagnosed disease) (P > 0.05). The overall ES for remission maintenance at the end of follow-up ranged between 51% and 91% (I2 = 74.8%). Subgroup meta-analysis identified kidney involvement as a possible source of heterogeneity, yielding a significantly higher rate of sustained remission in trials enrolling only patients with kidney involvement (92%, 76–100%) versus those enrolling patients with and without kidney involvement (56%, 45–66%). Results were similar in multiple sensitivity analyses. During follow-up, the frequency of SAEs in MMF-based treatment arms was 31.8%. Conclusions In AAV, MMF use was significantly associated with higher sustained remission rates in trials enrolling only patients with kidney involvement. These findings might influence clinical practice.

Abstract An international consensus on antineutrophil cytoplasm antibodies (ANCA) testing in eosinophilic granulomatosis with polyangiitis (EGPA) is presented. ANCA, specific for myeloperoxidase (MPO), can be detected in 30–35% of patients with EGPA. MPO-ANCA should be tested with antigen-specific immunoassays in any patient with eosinophilic asthma and clinical features suggesting EGPA, including constitutional symptoms; purpura; polyneuropathy; unexplained heart, gastrointestinal, or kidney disease; and/or pulmonary infiltrates or hemorrhage. A positive MPO-ANCA result contributes to the diagnostic workup for EGPA. Patients with MPO-ANCA–associated EGPA have vasculitis features, such as glomerulonephritis, neuropathy, and skin manifestations, more frequently than patients with ANCA-negative EGPA. However, the presence of MPO-ANCA is neither sensitive nor specific enough to identify whether a patient should be subclassified as having “vasculitic” or “eosinophilic” EGPA. At present, ANCA status cannot guide treatment decisions, that is, whether cyclophosphamide, rituximab, or mepolizumab should be added to conventional glucocorticoid treatment. In EGPA, monitoring of ANCA is only useful when MPO-ANCA was tested positive at disease onset.

Abstract 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.

ObjectiveIgG4‐related disease (IgG4‐RD) is a recently recognized disease characterized by fibroinflammatory infiltrates rich in IgG4+ plasma cells that can present as isolated tumor‐like lesions of the head and neck. The objective of the current study was to describe the cranial base manifestations of IgG4‐RD.MethodsReview of all cases at three tertiary‐referral centers since disease description in 2003.ResultsEleven patients were identified at a median age at presentation of 58 years (IQR, 38–65; 55% male). Ten (91%) patients had isolated skull base masses without systemic disease. Cranial neuropathies were commonly observed in the abducens (45%), trigeminal (18%), and facial nerves (18%). Lesions frequently involved the cavernous sinus (55%; 6/11) with extension to the petroclival junction in 50% (3/6). Infiltration of the internal auditory canal was present in 27% (3/11) with one case demonstrating erosion of the bony labyrinth. Preliminary clinical diagnoses commonly included nasopharyngeal cancer, pituitary macroadenoma, cholesteatoma, and meningioma / multiple meningioma syndrome. Local biopsy demonstrated >30 IgG4‐positive plasma cells per high‐powered field or an IgG4:IgG ratio greater than 40% in all cases. Rapid and durable clinical improvement was seen in 91% following corticosteroid and rituximab therapy.ConclusionsIgG4‐RD nonspecifically presents as a rare cause of the skull base mass. Often presenting without concomitant systemic disease, local diagnostic biopsies are required. Obtaining adequate tissue specimen is complicated by densely fibrotic cranial base lesions that are frequently in close proximity to critical neurovascular structures. Primary medical therapy with corticosteroids and rituximab is effective in most patients.Level of Evidence4 Laryngoscope, 130:2574–2580, 2020

Abstract BACKGROUND Erdheim-Chester disease (ECD) is a rare, non-Langerhans cell histiocytosis. Up to 50% of patients develop central nervous system involvement, and a subset of these patients can present with isolated tumor-like masses. OBJECTIVE To describe the skull base manifestations of ECD with an emphasis on aspects most pertinent to surgeons who may be referred such patients for primary evaluation. METHODS Scopus, Web of Science, and PubMed were searched from database inception to May 1, 2018 for articles reporting skull base ECD. An institutional retrospective analysis of all patients treated at the authors’ institution since January 1, 1996 was also performed to supplement these data. RESULTS Of 465 retrieved articles, 18 studies totaling 20 patients met inclusion criteria. Institutional review identified an additional 7 patients. Collectively, the median age at diagnosis was 49 yr (interquartile range, 42-58) with a 4:1 male-to-female ratio. Patients frequently presented with diplopia (48%), headache (30%), dysarthria (22%), and vertigo or imbalance (22%), though trigeminal hypesthesia (11%), facial nerve paresis (7%), hearing loss (7%), and trigeminal neuralgia (7%) were also observed. ECD commonly mimicked meningioma (33%), trigeminal schwannoma (8%), neurosarcoidosis (8%), and skull base lymphoma (8%). CONCLUSION Discrete skull base lesions frequently mimic more common pathology such as meningioma or cranial nerve schwannomas. Medical therapy comprises the initial treatment for symptomatic skull base disease. Surgical resection is not curative and the utility of surgical intervention is largely limited to biopsy to establish diagnosis and/or surgical debulking to relieve mass effect.

Significance Antigen recognition by the immune system triggers rapid, specific, and protective responses, which are counterbalanced by inhibitory checkpoints to minimize potentially harmful immunity. The programmed death-1/ programmed death ligand-1 (PD-1/PD-L1) checkpoint is overreactive in cancer patients, curbing antitumor immunity. Whether a failing PD-1/PD-L1 checkpoint contributes to spontaneous autoimmune disease in humans is unknown. Here, we found that in patients with the autoimmune vasculitis giant cell arteritis, antigen-presenting cells provide insufficient negative signaling; unleashing highly activated T cells to infiltrate and damage the walls of large arteries. Thus, immunoinhibitory signals protect large arteries against inflammatory attack and checkpoint activation may be a suitable strategy to treat autoimmune vasculitis.