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Trained immunity (TI) is a proinflammatory program induced in monocyte/macrophages upon sensing of specific pathogens and is characterized by immunometabolic and epigenetic changes that enhance cytokine production. Maladaptive activation of TI (ie, in the absence of infection) may result in detrimental inflammation and development of disease; however, the exact role and extent of inappropriate activation of TI in the pathogenesis of human diseases is undetermined. In this study, we uncovered the 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/mammalian target of rapamycin signaling axis; increased glycolysis, glutaminolysis, and cholesterol synthesis; epigenetic changes on promoters of genes encoding cytokines; and enhanced cytokine production leading to hyperinflammatory responses. In patients with ECD, effective therapeutic strategies combat this maladaptive TI phenotype; in addition, pharmacologic inhibition of immunometabolic changes underlying TI (ie, glycolysis) effectively dampens cytokine production by myeloid cells. This study revealed 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., (© 2021 by The American Society of Hematology.)

Erdheim-Chester disease is a rare form of non-Langerhans histiocytosis. A 40-year-old woman was diagnosed as Erdheim-Chester disease based on typical bone scintigraphy, symmetric osteosclerosis and findings of foamy, non-Langerhans histiocytes in bone marrow. BRAF V600E mutation was detected in a bone biopsy. Treatment with IFN-α showed significant improvement. The BRAF V600E mutant was detected in plasma cell-free DNA (cfDNA) by a droplet-digital PCR assay. Longitudinal analysis of BRAF V600E in plasma cfDNA showed a decreasing trend during treatment. We could not detect the mutant in urinary cfDNA. While, similar studies have detected the BRAF V600E mutant in urine, but not in plasma. A combination of allele burden assessments in plasma and urine may be helpful for detecting the residual mutant burden and monitoring therapeutic response.

Langerhans cell histiocytosis (LCH) and the non-LCH neoplasm Erdheim-Chester disease (ECD) are heterogeneous neoplastic disorders marked by infiltration of pathologic macrophage-, dendritic cell-, or monocyte-derived cells in tissues driven by recurrent mutations activating MAPK signaling. Although recent data indicate that at least a proportion of LCH and ECD patients have detectable activating kinase mutations in circulating hematopoietic cells and bone marrow-based hematopoietic progenitors, functional evidence of the cell of origin of histiocytosis from actual patient materials has long been elusive. Here, we provide evidence for mutations in MAPK signaling intermediates in CD34 + cells from patients with ECD and LCH/ECD, including detection of shared origin of LCH and acute myelomonocytic leukemia driven by TET2 -mutant CD34 + cell progenitors in one patient. We also demonstrate functional self-renewal capacity for CD34 + cells to drive the development of histiocytosis in xenotransplantation assays in vivo. These data indicate that the cell of origin of at least a proportion of patients with systemic histiocytoses resides in hematopoietic progenitor cells prior to committed monocyte/macrophage or dendritic cell differentiation and provide the first example of a patient-derived xenotransplantation model for a human histiocytic neoplasm., (© 2017 by The American Society of Hematology.)

Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD) are rare histiocytic disorders induced by somatic mutation of MAPK pathway genes. BRAF V600E mutation is the most common mutation in both conditions and also occurs in the hematopoietic neoplasm hairy cell leukemia (HCL). It is not known if adult LCH or ECD arises from hematopoietic stem cells (HSCs), nor which potential blood borne precursors lead to the formation of histiocytic lesions. In this study, BRAF V600E allele-specific polymerase chain reaction was used to map the neoplastic clone in 20 adults with LCH, ECD, and HCL. BRAF V600E was tracked to classical monocytes, nonclassical monocytes, and CD1c + myeloid dendritic cells (DCs) in the blood, and mutations were observed in HSCs and myeloid progenitors in the bone marrow of 4 patients. The pattern of involvement of peripheral blood myeloid cells was indistinguishable between LCH and ECD, although the histiocytic disorders were distinct to HCL. As reported in children, detection of BRAF V600E in peripheral blood of adults was a marker of active multisystem LCH. The healthy counterparts of myeloid cells affected by BRAF mutation had a range of differentiation potentials depending on exogenous signals. CD1c + DCs acquired high langerin and CD1a with granulocyte-macrophage colony-stimulating factor and transforming growth factor β alone, whereas CD14 + classical monocytes required additional notch ligation. Both classical and nonclassical monocytes, but not CD1c + DCs, made foamy macrophages easily in vitro with macrophage colony-stimulating factor and human serum. These studies are consistent with a hematopoietic origin and >1 immediate cellular precursor in both LCH and ECD., (© 2017 by The American Society of Hematology.)

Erdheim-Chester disease (ECD) is a rare form of non-Langerhans cell histiocytosis, which is known to affect various organs; however, there have been no reports of its intrapelvic involvement. We herein describe the case of 69-year-old man who died of a rapidly-growing intrapelvic tumor, which was finally diagnosed as ECD at autopsy. Immunohistochemically, the tumor cells were positive for CD68 and BRAF V600E, and negative for CD1a. Since BRAF V600E has recently been reported to be specific to ECD, it can be a useful biomarker for diagnosis, especially in atypical cases.

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis characterized by multisystem infiltration by foamy histiocytes surrounded by fibrosis. ECD often involves the long bones, skin, and retroperitoneum, whereas breast involvement is very rare with only 6 reported cases in English literature. We report a case of ECD presenting within the right breast as a clinically malignant tumor, in addition to bilateral sclerotic lesions of the femurs, bilateral soft tissue masses of the cerebellum, and multiple subcutaneous nodules on the abdominal wall in a 61-year-old woman. Histologically, there was a prominent infiltrate of foamy histiocytes with scattered Touton-type giant cells, lymphocytes, and plasma cells. The foamy histiocytes were arranged in small clusters or scattered singly in the background of fibrosis. However, in some areas, there was a prominent proliferation of fibrosis with scant cellular infiltrate including histiocytes. The diagnosis of ECD was made by characteristic histopathologic features in addition to clinical-radiographic features and the typical immunoprofile (positive for cluster of differentiation 68 [CD68], CD163, and p16; negative for CD1a and S-100). Although rare, ECD must be considered in the differential diagnosis of clinically malignant tumor of the breast. To our knowledge, this is the second case of ECD involving the breast in which a valine 600 glutamic acid mutation was detected, which probably represents a clonal disorder of non-Langerhans cells., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Objective: To explore the clinicopathologic features, immunophenotype, differential diagnosis and gene mutation status of the Erdheim-Chester disease (ECD)., Methods: Clinical and pathologic findings of 3 ECD cases were examined by gross, microscopic, immunohistochemical methods and BRAF V600E mutation. Related literatures were reviewed., Results: Two male patients and one female patient presented clinically with multiple skin nodules, bone pain and bony lesions by imaging study. Microscopically, the lesions were composed of spindle-shaped fibroblasts, foamy histiocytes and scattered Touton-type giant cells embedded in reactive fibrous tissue. Lymphocytes, plasma cells, and multinucleated giant cells were also found. Immunohistochemically, all histiocytes were positive for CD68, none of which expressed CD1a, although 2 cases focally expressed weak S-100 stain. In 2 cases,BRAF V600E mutation was detected., Conclusions: ECD is a rare disease of xanthogranulomatous histiocytosis.Its diagnosis relies on pathological and immunohistochemical findings, but correlation with clinical information, especially radiographic findings should be performed.No effective treatment of the disease is currently available.

We treated a 77-year-old woman with pleural and pericardial effusion and ascites. Initially, collagen vascular disease was suspected due to the presence of anti-centromere antibodies and suspected complication of pulmonary arterial hypertension. However, soft-tissue abnormalities surrounding the bilateral kidneys detected on computed tomography (CT) and symmetrical lesions of the long bones detected on bone scintigraphy made us consider a diagnosis of Erdheim-Chester disease (ECD), which is a rare form of histiocytosis. We immunochemically analyzed the cells derived from the ascites in detail and confirmed the diagnosis. Immunocytochemical analyses may therefore help to achieve a better understanding of the pathogenesis of this rare disease.

Immunopathogenesis of Erdheim-Chester disease (ECD), a rare non-Langerhans cell histiocytosis, is poorly known. In previous studies, various cytokines were detected in ECD lesions, presumably orchestrating lesional histiocyte recruitment. Because ECD lesions are frequently associated with systemic symptoms, we postulated that underlying global immune perturbations might also be revealed. We quantitatively analyzed 23 cytokines in serum samples obtained from a large single-center cohort of 37 patients with ECD, and studied the impact of treatment on cytokine production. IL-6, IL-12, interferon-α (IFN-α), and monocyte chemotactic protein-1 (MCP-1) levels were significantly higher in untreated patients than in controls, whereas interferon-γ (IFN-γ) inducible protein 10, IL-12, MCP-1, and IL-1 receptor antagonist were found significantly increased in IFN-α-treated patients. A biomathematical approach was used to rationalize multiparameter data, to generate new hypotheses, and identify global control pathways. Interestingly, cytokine profiles proved to be particularly stable at the individual level, and an "ECD signature" further distinguished patients from controls, based on their production of IFN-α, IL-12, MCP-1, IL-4, and IL-7. Altogether, our data underline the systemic immune Th-1-oriented perturbation associated with this condition and provide clues for the choice of more focused therapeutic agents in this rare disease with noncodified therapeutic management.

Erdheim-Chester disease (ECD) is a rare non-Langherans form of histiocytosis characterized radiologically by symmetrical sclerosis of the metaphysis and the diaphysis of long tubular bones. Macrophages are potent interleukin-6 (IL-6) producers and elevated IL-6 serum levels have been described in pathological conditions characterized by increased bone resorption. In a patient with ECD, during the acute phase of the disease we found high serum levels of IL-6 and IL-6 soluble receptor (sIL-6R) and high levels of bone turnover markers. After 5 years of combination therapy with oral prednisone and intravenous clodronate a significant reduction in the above mentioned biological parameters was seen. We suggest that the systemic disorders present in ECD could be related to the high serum levels of IL-6 and sIL-6R. We also propose the use of bisphosphonates in the clinical management of ECD.