Erdheim-Chester disease as complex clinical presentation and diagnosis: A case report and concise review of literature

RATIONALE

Erdheim-Chester disease (ECD) is a rare multisystemic disease characterized by the infiltration of multiple organs by foamy CD68 + CD1a-histiocytes. The genetic background consists of gain-of-function somatic mutations in the mitogen-activated protein kinase pathway. The purpose of the present paper is to make a contribution to the scientific literature on ECD by reporting our experience with a complex clinical case report, along with a concise review of the literature. We discussed the unusual clinical presentation, the complex diagnostic process and the comparison with other published cases.

PATIENT CONCERNS

A 70-year-old man presented with arthralgia due to multiple bone areas of sclerosis, first diagnosed with metastases of a prostatic neoplasm. Sequential thorax-abdomen, femoral and homer contrast-enhanced computed tomography (CT) showed pericardial effusion, pulmonary fibrosis, and perirenal fibrous tissue as "hairy kidneys." He underwent. Three bone biopsies were unsuccessful to reach diagnosis.

DIAGNOSES

A xanthelasma biopsy showed histopathological signs compatible with ECD; genetic analysis showed the mutation BRAFV600E.

INTERVENTIONS

The patient underwent targeted therapy with vemurafenib (BRAF-inhibitor), discontinued 2 weeks later due to the onset of a diffuse erythematous papular rash on the trunk and limbs.

OUTCOMES

At the 1-year follow-up, there was only progression of chronic kidney disease (CKD).

LESSONS

The present case report describes how ECD diagnosis could represent a challenge for clinicians, owing to its heterogeneous clinical presentation. Early diagnosis followed by prompt therapy is essential for modifying the natural history of the disease.

[Central nervous system disorders secondary to histiocytoses: neurodegeneration with potential for improvement]

Histiocytoses, including Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD), are inflammatory myeloid tumors in which monocyte lineage cells aggregate in various organs, causing tissue damage. Most of these tumors harbor oncogenic mutations in mitogen-activated protein kinase (MAPK) pathway genes, typified by BRAFV600E. Some patients with LCH develop bilateral symmetrical cerebellar lesions and brain atrophy several years after diagnosis when the initial symptoms disappear, leading to cerebellar ataxia and higher cerebral dysfunction. A similar neurological disorder has also been reported in ECD. This neurological disorder can be improved with MAPK inhibitors. When patients with this neurological disorder are identified among neurodegeneration of unknown etiology or histiocytosis patients and treated early with MAPK inhibitors, the disorder can be reversible.

Skeletal involvement in Erdheim-Chester disease: Multimodality imaging features and association with the BRAFV600E mutation

OBJECTIVE

The aim of this study was to characterize the distribution of skeletal involvement in Erdheim-Chester disease (ECD) by using radiography, computed tomography (CT), 18F-FDG positron emission tomography/computed tomography (PET/CT), and bone scans, as well as looking for associations with the BRAFV600E mutation.

MATERIAL AND METHODS

Prospective study of 50 consecutive patients with biopsy-confirmed ECD who had radiographs, CT, 18F-FDG PET/CT, and Tc-99m MDP bone scans. At least two experienced radiologists with expertise in the relevant imaging studies analyzed the images. Summary statistics were expressed as the frequency with percentages for categorical data. Fisher's exact test, as well as odds ratios (OR) with 95 % confidence intervals (CI), were used to link imaging findings to BRAFV600E mutation. The probability for co-occurrence of bone involvement at different locations was calculated and graphed as a heat map.

RESULTS

All 50 cases revealed skeletal involvement at different regions of the skeleton. The BRAFV600E mutation, which was found in 24 patients, was correlated with femoral and tibial involvement on 18F-FDG PET/CT and bone scan. The appearance of changes on the femoral, tibial, fibular, and humeral involvement showed correlation with each other based on heat maps of skeletal involvement on CT.

CONCLUSION

This study reports the distribution of skeletal involvement in a cohort of patients with ECD. CT is able to detect the majority of ECD skeletal involvement. Considering the complementary nature of information from different modalities, imaging of ECD skeletal involvement is optimized by using a multi-modality strategy.

The role of 2-[18F]FDG PET/CT in Erdheim-Chester disease

OBJECTIVE

To analyze the body distribution of Erdheim-Chester disease (ECD) and determine the utility of 2-[18 F]FDG PET/CT compared to other imaging techniques. Additionally, to assess the aggressiveness and extent of the disease based on the presence/absence of the BRAFV600E mutation.

MATERIALS AND METHODS

The 2-[18F]FDG-PET/CT scans of all patients diagnosed with ECD between 2008 and 2021 were reviewed, including 19 patients. The affected territories were classified as detectable by PET/CT or detectable only by other imaging techniques (bone scintigraphy, contrast-enhanced CT, or MRI). Descriptive analysis and correlation of the BRAF mutation with the affected organs and maximum SUV were performed using the Student's t-test.

RESULTS

Out of the 19 patients (14 males; mean age 60.3 years), 11 had the BRAFV600E mutation. A total of 127 territories (64 organ-systems) affected were identified using different imaging modalities, of which 112 were detected by PET/CT, and an additional 15 territories were solely identified by cerebral and cardiac MRI. The presence of BRAFV600E mutation was associated with greater organ involvement (p < 0.05) without differences in SUVmax (p > 0.05).

CONCLUSION

2-[18F]FDG PET/CT is a highly effective diagnostic tool in patients with ECD, detecting the majority of affected territories. MRI was the only imaging modality with additional findings in territories showing high physiological uptake of 2-[18F]FDG (cerebral and cardiac). The presence of the BRAFV600E mutation correlated with a higher extent of the disease.

Genome-Wide Association Study Identifies the First Germline Genetic Variant Associated With Erdheim-Chester Disease

OBJECTIVE

Erdheim-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.

METHODS

After 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.

RESULTS

A 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.

CONCLUSION

Overall, this work demonstrates that germline genetic variants can impact on the development of ECD and suggests new pathways with a potential pathogenic role.

The clinical spectrum and prognostic factors of Erdheim-Chester disease and mixed Langerhans cell histiocytosis and Erdheim-Chester disease

Erdheim-Chester disease (ECD) is a rare and probably fatal multisystemic non-Langerhans cell histiocytosis (LCH). To comprehensively investigate the clinical features, genomic analysis, treatments, and prognostic factors of ECD, we retrospectively analyzed the clinical data of 75 ECD patients and 10 mixed LCH and ECD patients in our center. The median age at diagnosis was 46 years (range, 5-70). ECD patients were older at diagnosis (p = 0.006) and had more cardiac involvement (p = 0.011) as well as vascular (p = 0.031) involvement compared to mixed LCH and ECD patients. 64.8% of ECD patients and 87.5% of mixed LCH and ECD patients carried BRAFV600E mutation. The BRAFV600E mutation correlated with a greater number of affected organs (p = 0.030) and was associated with lung involvement (p = 0.033) as well as pleural involvement (p = 0.002). The median follow-up time was 38 months (range, 1-174). The estimated 5-year progression-free survival (PFS) and overall survival (OS) were 48.9% and 84.7%, respectively. In a multivariate analysis, right atrial pseudotumor (p = 0.013) and pancreatic involvement (p = 0.005) predicted worse OS, while pleural (p = 0.042) and central nervous system (CNS) involvement (p = 0.043) predicted worse PFS. Our study described the clinical spectrum of ECD and mixed LCH and ECD, while also revealed the prognostic value of right atrial pseudotumor and pancreatic, pleural, and CNS involvement for worse survival.

Erdheim-Chester Disease Involving the Left Uterine Adnexa: Mimicking an Ovarian Carcinoma Clinically

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis (LCH) that results in multiorgan disease involving the skin, bones, lungs, and kidneys. Female reproductive system manifestation of ECD was rare. Herein, we report a case of ECD involving the left ovary and fallopian tube. A 69-year-old woman presented with abdominal pain for 20 days. Magnetic resonance imaging revealed a solid and cystic mass on the left pelvic cavity. Histological examination revealed ovarian and fallopian tube infiltration by abundant histiocytes, with single small nuclei and foamy cytoplasm, reactive small lymphocytes, and plasma cells. Based on histopathological and immunohistochemical findings of positivity for CD68, CD163, and BRAF V600E and negativity for CD1α and S100, the molecular finding of BRAF V600E mutation, the patient was diagnosed with ECD. Positron emission tomography examination did not reveal any other lesions. The patient recovered well 12 months after surgery without any treatment. ECD involving the left fallopian tube and ovary was rare and needed to be differentiated from LCH, Rosai-Dorfman disease (RDD), juvenile xanthogranuloma (JXG), IgG4+-related disease (IgG4+RD), and metastatic signet ring cell carcinoma.

Erdheim-Chester Disease Due to a Novel Internal Duplication of NRAS: Response to Targeted Therapy with Cobimetinib

Histiocytoses encompass a group of exceptionally rare disorders characterized by the abnormal infiltration of tissues by histocytes. Among these, Erdheim-Chester disease (ECD) stands out as a multisystem histiocytosis that typically affects bones and various other tissues. Historically, the treatment of ECD has been challenging. However, recent breakthroughs in our understanding, particularly the discovery of somatic mutations in the RAS-MAPK pathway, have opened new opportunities for targeted therapy in a significant subset of patients with ECD and other histiocytoses. In this report, we present the case of a patient with ECD harboring a previously unidentified microduplication in the NRAS gene in a small fraction of skin cells. This discovery played a pivotal role in tailoring an effective therapeutic approach involving kinase inhibitors downstream of NRAS. This case underscores the crucial role of deep sequencing of tissue samples in ECD, enabling the delivery of personalized targeted therapy to patients.

An effective treatment in Erdheim Chester disease: vemurafenib: a case report

BACKGROUND

Erdheim Chester disease (ECD) is a rare disease with multisystemic involvement in the group of non-langerhans cell histiocytosis. Although nearly 100 years have passed since its definition, the number of cases reported all over the world is below 1000. In addition to the rarity of the disease, low awareness seems to play a role in this.

CASE PRESENTATION

47-year-old white caucasian women patient who presented to our clinic with symptoms of weakness-fatigue as well as increasing pain in the knees and ptosis in the left eye. Result of the patient's bone biopsy, ECD was considered pathologically and BRAF V600E mutation was shown molecularly. After presenting the clinical, laboratory and other examination results of the case, the dramatic response seen with targeted therapy will be discussed.

CONCLUSIONS

BRAF V600E mutation is frequently seen in ECD. Vemurafenib plays an active role in targeted therapy.

Impact of BRAFV600E mutation on aggressiveness and outcomes in adult clonal histiocytosis

Histiocytoses encompass a wide spectrum of diseases, all characterized by tissue infiltration by CD68+ histiocytes. Most adult histiocytoses are considered clonal diseases because they highlight recurrent somatic mutations in the MAP-kinase pathway gene, primarily BRAF. The presence of BRAF mutation is associated with widespread disease in children with Langerhans cell histiocytosis (LCH) or cardiovascular/neurological involvement in Erdheim-Chester disease (ECD). Nevertheless, few data are available on adult clonal histiocytosis. This is why we have conducted a retrospective study of all patients with clonal histiocytosis in our institution and present the data according to the presence of BRAF mutation. Among 27 adult patients (10 ECD, 10 LCH, 5 Rosai-Dorfman disease (RDD), and 3 mixed ECD/LCH), 11 (39%) have BRAF mutation with gain of function (n = 9) and deletion (n = 2). Those patients had frequent multicentric disease with risk organ involvement, especially the brain and cardiovascular system. They had frequent associated myeloid neoplasms (mostly chronic myelomonocytic leukemia) and received more frequently targeted therapy as the front-line therapy. Nevertheless, its presence did not affect the overall survival or relapse-free survival probably due to the emergence of efficient therapies. To conclude, rapid and accurate molecular establishment in adult clonal histiocytoses is crucial because BRAFV600E mutation correlates with multicentric disease with organ involvement and incomplete metabolic response.

Successful treatment of non-Langerhans cell histiocytosis with the MEK inhibitor trametinib: a multicenter analysis

Erdheim-Chester disease (ECD) and Rosai-Dorfman disease (RDD) are rare non-Langerhans cell histiocytoses (non-LCHs), for which therapeutic options are limited. MAPK pathway activation through BRAFV600E mutation or other genomic alterations is a histiocytosis hallmark and correlates with a favorable response to BRAF inhibitors and the MEK inhibitor cobimetinib. However, there has been no systematic evaluation of alternative MEK inhibitors. To assess the efficacy and safety of the MEK inhibitor trametinib, we retrospectively analyzed the outcomes of 26 adult patients (17 with ECD, 5 with ECD/RDD, 3 with RDD, and 1 with ECD/LCH) treated with orally administered trametinib at 4 major US care centers. The most common treatment-related toxicity was rash (27% of patients). In most patients, the disease was effectively managed at low doses (0.5-1.0 mg trametinib daily). The response rate of the 17 evaluable patients was 71% (73% [8/11] without a detectable BRAFV600E achieving response). At a median follow-up of 23 months, treatment effects were durable, with a median time-to-treatment failure of 37 months, whereas the median progression-free and overall survival were not reached (at 3 years, 90.1% of patients were alive). Most patients harbored mutations in BRAF (either classic BRAFV600E or other BRAF alterations) or alterations in other genes involved in the MAPK pathway, eg, MAP2K, NF1, GNAS, or RAS. Most patients required lower than standard doses of trametinib but were responsive to lower doses. Our data suggest that the MEK inhibitor trametinib is an effective treatment for ECD and RDD, including those without the BRAFV600E mutation.

Erdheim-Chester Disease: A Case Report of BRAF V600E-Negative, MAP2K1-Positive ECD Diagnosed by Blood Next-Generation Sequencing Assay and a Brief Literature Review

Erdheim-Chester disease (ECD) is a rare type of non-Langerhans cell histiocytosis. However, its prevalence has increased significantly the past few years due to increased awareness about the disorder, and 1500 cases have been reported worldwide. It is often a multisystemic disease with skeletal, cardiovascular, urologic, renal, retroperitoneal, pulmonary, endocrine, cutaneous, and neurologic involvement. MAPK pathway mutations, such as BRAF activating and MAP2K1 mutations, play a key role in its pathogenesis. In addition to the characteristic clinical, radiological, and histopathological findings, identifying underlying mutations helps diagnose and treat patients with highly effective targeted therapies such as BRAF and MEK inhibitors. We report a case of a man, aged 55 years, with an extensive and prolonged course of an unexplained multisystemic disease, later diagnosed with BRAF V600E-negative and MAP2K1-positive ECD on cell-free DNA testing. Additionally, we review common clinical manifestations, mutations, diagnoses, and targeted therapies for ECD.

Prevalence, patterns and outcomes of cardiac involvement in Erdheim-Chester disease

AIMS

Cardiac involvement of Erdheim-Chester disease (ECD), a rare L group histiocytosis, has been reported to be associated with poor outcomes, but systematic studies are lacking. The present study aimed to investigate the prevalence, clinical features, imaging features, and prognosis of cardiac involvement in ECD in a large series.

METHODS AND RESULTS

All patients with ECD who underwent cardiac magnetic resonance (CMR) imaging between 2003 and 2019 at a French tertiary center were retrospectively included. Primary outcome was all-cause mortality. Secondary outcomes were pericarditis, cardiac tamponade, conduction disorders, device implantation and coronary artery disease (CAD). A total of 200 patients were included [63 (54-71) years, 30% female, 58% BRAFV600E mutated]. Median follow-up was 5.5 years (3.3-9 years). On CMR, right atrioventricular sulcus infiltration was observed in 37% of patients, and pericardial effusion was seen in 24% of patients. In total, 8 patients (4%) had pericarditis (7 acute, 1 constrictive), 10 patients (5%) had cardiac tamponade, 5 patients (2.5%) had ECD-related high-degree conduction disorders, and 45 patients (23%) had CAD. Overall, cardiac involvement was present in 96 patients (48%) and was associated with BRAFV600E mutation [Odds ratio (OR) = 7.4, 95% confidence interval (CI) (3.5-16.8), P < 0.001] and ECD-related clinical events [OR = 5, 95%CI (1.5-21.2), P = 0.004] but not with lower survival in multivariate analysis [adjusted hazard ratio (HR) = 1.4, 95% CI (0.8-2.5), P = 0.2].

CONCLUSION

Cardiac involvement is present in nearly half of ECD patients and is associated with BRAFV600E mutation and complications (pericarditis, cardiac tamponade, and conduction disorders) but not with lower survival.

Molecular and clinicopathologic characterization of pediatric histiocytoses

The spectrum of somatic mutations in pediatric histiocytoses and their clinical implications are not fully characterized, especially for non-Langerhans cell histiocytosis (-LCH) subtypes. A cohort of 415 children with histiocytosis from the French histiocytosis registry was reviewed and analyzed for BRAFV600E . Most BRAFWT samples were analyzed by next-generation sequencing (NGS) with a custom panel of genes for histiocytosis and myeloid neoplasia. Of 415 case samples, there were 366 LCH, 1 Erdheim-Chester disease, 21 Rosai-Dorfman disease (RDD), 21 juvenile xanthogranuloma (JXG, mostly with severe presentation), and 6 malignant histiocytosis (MH). BRAFV600E was the most common mutation found in LCH (50.3%, n = 184). Among 105 non-BRAFV600E -mutated LCH case samples, NGS revealed mutations as follows: MAP2K1 (n = 44), BRAF exon 12 deletions (n = 26), and duplications (n = 8), other BRAF V600 codon mutation (n = 4), and non-MAP-kinase pathway genes (n = 5). Wild-type sequences were identified in 17.1% of samples. BRAFV600E was the only variant significantly correlated with critical presentations: organ-risk involvement and neurodegeneration. MAP-kinase pathway mutations were identified in seven RDD (mostly MAP2K1) and three JXG samples, but most samples were wild-type on NGS. Finally, two MH samples had KRAS mutations, and one had a novel BRAFG469R mutation. Rarely, we identified mutations unrelated to MAP-kinase pathway genes. In conclusion, we characterized the mutational spectrum of childhood LCH and clinical correlations of variants and subtypes. Variants responsible for JXG and RDD were not elucidated in more than half of the cases, calling for other sequencing approaches.

Erdheim-Chester disease and vemurafenib: a review of ophthalmic presentations and clinical outcomes

PURPOSE

To provide a comprehensive review of ocular and orbital manifestations of Erdheim-Chester Disease (ECD) and compare clinical outcomes with vemurafenib (INN) to historical treatments (HT). Primary outcomes are ophthalmic findings on presentation, changes in visual acuity, and mortality rate. Secondary outcomes include the progression of ocular findings, systemic involvements, and treatment modalities.

METHODS

All published literature from January 1983 to March 2021 was searched for ophthalmic manifestations of ECD. Clinical outcomes following HT were collected and compared with INN.

RESULTS

Forty-seven patients with ECD and ophthalmic presentations were identified. The mean age was 49.6 years (SD = 15.0). Proptosis (65.6%) and extraocular muscle restrictions (42.5%) were the most common presenting signs. Of 41 (87.2%) patients with orbital masses on radiologic examination, 90.2% were bilateral, and 53.7% were located in the intraconal space. Ophthalmic examination was significant for xanthelasma (27.2%), optic disc edema (34.0%), and subretinal changes (21.3%). Common treatments were systemic steroids (76.6%), interferon-α (17.0%), and cyclophosphamide (14.9%). INN was less commonly used (12.8%). The mean change in logMAR visual acuity declined with HT (29.9%) but improved with INN (79.1%) (p > 0.05). The proportion of eyes with complete vision loss increased after HT (p < 0.05). The overall mortality rate was 27.7% and notably higher in the HT group (29.3%) when compared to the INN group (16.7%) (p > 0.05).

CONCLUSION

ECD presents with many ophthalmic manifestations. Although the intraocular treatments remain controversial, INN should be highly considered in treating orbital ECD patients with BRAF-V600E mutations to prevent and reverse vision loss.

Erdheim-Chester disease: First pediatric case report in Colombia

The Erdheim-Chester’s disease is extremely rare in children. We present the case of a 12-year-old girl with histological and radiological diagnosis of this disease and mutation of the BRAF gene, who developed multisystemic compromise requiring treatment with dabrafenib. We identified 22 reports of this condition among children worldwide and this is the second pediatric case in Latin America. Diagnostic imaging is critical to confirm Erdheim-Chester disease and for the surgical planning of the biopsy. Additionally, we identified the parasellar dark sign, which has previously been reported on lymphocytic hypophysitis. This report contributes to the current practice as it shows the clinical presentation and the diagnostic workout of this disease in pediatrics.

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.

MAP-Kinase-Driven Hematopoietic Neoplasms: A Decade of Progress in the Molecular Age

Mutations in members of the mitogen-activated protein kinase (MAPK) pathway are extensively studied in epithelial malignancies, with BRAF mutations being one of the most common alterations activating this pathway. However, BRAF mutations are overall quite rare in hematological malignancies. Studies over the past decade have identified high-frequency BRAF V600E, MAP2K1, and other kinase alterations in two groups of MAPK-driven hematopoietic neoplasms: hairy cell leukemia (HCL) and the systemic histiocytoses. Despite HCL and histiocytoses sharing common molecular alterations, these are phenotypically distinct malignancies that differ in respect to clinical presentation and suspected cell of origin. The purpose of this review is to highlight the molecular advancements over the last decade in the histiocytic neoplasms and HCL and discuss the impact these insights have had on our understanding of the molecular pathophysiology, cellular origins, and therapy of these enigmatic diseases as well as perspectives for future research directions.

Erdheim-Chester Disease and Langerhans Cell Histiocytosis: A Case of Overlap Syndrome

Only 500 cases of Erdheim‐Chester disease have been reported in the literature to date. To increase awareness of this rare disease, this letter to the editor describes the unusual case of a woman who was diagnosed with mixed histiocytosis: Erdheim‐Chester disease and Langerhans cell histiocytosis.

Spectrum of histiocytic neoplasms associated with diverse haematological malignancies bearing the same oncogenic mutation

Histiocytic disorders are a spectrum of rare diseases characterised by the accumulation of macrophage-, dendritic cell-, or monocyte-differentiated cells in various tissues and organs. The discovery of recurrent genetic alterations in many of these histiocytoses has led to their recognition as clonal neoplastic diseases. Moreover, the identification of the same somatic mutation in histiocytic lesions and peripheral blood and/or bone marrow cells from histiocytosis patients has provided evidence for systemic histiocytic neoplasms to originate from haematopoietic stem/progenitor cells (HSPCs). Here, we investigated associations between histiocytic disorders and additional haematological malignancies bearing the same genetic alteration(s) using the nationwide Dutch Pathology Registry. By searching on pathologist-assigned diagnostic terms for the various histiocytic disorders, we identified 4602 patients with a putative histopathological diagnosis of a histiocytic disorder between 1971 and 2019. Histiocytosis-affected tissue samples of 187 patients had been analysed for genetic alterations as part of routine molecular diagnostics, including from nine patients with an additional haematological malignancy. Among these patients, we discovered three cases with different histiocytic neoplasms and additional haematological malignancies bearing identical oncogenic mutations, including one patient with concomitant KRAS p.A59E mutated histiocytic sarcoma and chronic myelomonocytic leukaemia (CMML), one patient with synchronous NRAS p.G12V mutated indeterminate cell histiocytosis and CMML, and one patient with subsequent NRAS p.Q61R mutated Erdheim-Chester disease and acute myeloid leukaemia. These cases support the existence of a common haematopoietic cell-of-origin in at least a proportion of patients with a histiocytic neoplasm and additional haematological malignancy. In addition, they suggest that driver mutations in particular genes (e.g. N/KRAS) may specifically predispose to the development of an additional clonally related haematological malignancy or secondary histiocytic neoplasm. Finally, the putative existence of derailed multipotent HSPCs in these patients emphasises the importance of adequate (bone marrow) staging, molecular analysis and long-term follow-up of all histiocytosis patients.

Erdheim-Chester disease

Erdheim-Chester disease is a rare inflammatory myeloid clonal disease which is classified into histiocytoses. It is characterized by excessive production and accumulation of foamy histiocytes and Touton giant cells in various tissues and organs. Foamy histiocytes and Touton giant cells produce proinflammatory cytokines and chemokines and contain somatic mutations in genes activating the MAPK/ERK signaling pathway, but also in genes activating the PI3K/AKT signaling pathway. BRAFV600E is the most common somatic mutation. Furthermore, somatic mutations in the MAP2K1, KRAS, NRAS, ARAF or PIK3CA genes are abundant. Erdheim-Chester dis-ease is a multisystemic disease in which any organ can be affected, especially the long bones of the lower extremities, but also the cardiovascular system, retroperitoneum, endocrine system, central nervous system, lungs, skin or orbit. The dia-gnosis is difficult because of the various manifestations of this disease. The disease occurs mainly in adults and is more common in men than in women. Targeted treatment by kinase inhibitors, interferon a, cytokine blockers or cladribine is used for the treatment.

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 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.

[Erdheim-Chester disease : a case report]

We report the case of a 47-year-old woman with unexplained inflammatory syndrome and asthenia. Imaging findings show bilateral abnormalities of femurs and tibias, suggesting an Erdheim-Chester disease, which is confirmed by a bone marrow biopsy of the left femur. The BRAF V600E mutation is detected, allowing the administration of targeted therapies such as BRAF and MEK inhibitors that lead to the improvement of symptoms.

A rare differential for sinusitis and visual loss

Erdheim-Chester disease is a rare infiltrative histiocytic disorder with around 800 cases being reported worldwide. Patients most commonly present with skeletal pain, but the condition has been shown to affect multiple other organs. We describe a rare presentation in which the disease infiltrated the sinuses and affected an ex-RAF pilot's vision. After extensive investigation of the elusive diagnosis, repeating of a molecular test using polymerase chain reaction analysis allowed for identification of a mutation (BRAF V600) ultimately leading to the diagnosis of Erdheim-Chester disease.

Real-World Toxicity Experience with BRAF/MEK Inhibitors in Patients with Erdheim-Chester Disease

Background

Erdheim‐Chester disease (ECD) is a rare non‐Langerhans cell histiocytosis. The BRAF inhibitor vemurafenib is approved by the U.S. Food and Drug Administration (FDA) for patients with ECD harboring a BRAF V600E mutation. Successful treatment has also been reported with MEK‐targeted therapies, likely because of the fact that BRAF mutant–negative patients harbor MEK pathway alterations. In our Rare Tumor Clinic, we noted that these patients have frequent drug‐related toxicity, consistent with previous reports indicating the need to markedly lower doses of interferon‐alpha when that agent is used in these patients.

Patients and Methods

We performed a review of ten patients with ECD seen at the Rare Tumor Clinic at University of California San Diego receiving 16 regimens of targeted BRAF, MEK, or combined therapies.

Results

The median age of the ten patients with ECD was 53 years (range, 29–77); seven were men. The median dose percentage (percent of FDA‐approved dose) tolerated was 25% (range, 25%–50%). The most common clinically significant adverse effects resulting in dose adjustments of targeted therapies were rash, arthralgias, and uveitis. Renal toxicity and congestive heart failure were seen in one patient each. In spite of these issues, eight of ten patients (80%) achieved a partial remission on therapy.

Discussion

Patients with ECD appear to require substantially reduced doses of BRAF and MEK inhibitors but are responsive to these lower doses.

This brief communication describes real‐world toxicity and required dose adjustments of BRAF/MEK inhibitors for patients with Erdheim‐Chester disease.

BRAF V600E mutation in Juvenile Xanthogranuloma family neoplasms of the central nervous system (CNS-JXG): a revised diagnostic algorithm to include pediatric Erdheim-Chester disease

The family of juvenile xanthogranuloma family neoplasms (JXG) with ERK-pathway mutations are now classified within the "L" (Langerhans) group, which includes Langerhans cell histiocytosis (LCH) and Erdheim Chester disease (ECD). Although the BRAF V600E mutation constitutes the majority of molecular alterations in ECD and LCH, only three reported JXG neoplasms, all in male pediatric patients with localized central nervous system (CNS) involvement, are known to harbor the BRAF mutation. This retrospective case series seeks to redefine the clinicopathologic spectrum of pediatric CNS-JXG family neoplasms in the post-BRAF era, with a revised diagnostic algorithm to include pediatric ECD. Twenty-two CNS-JXG family lesions were retrieved from consult files with 64% (n = 14) having informative BRAF V600E mutational testing (molecular and/or VE1 immunohistochemistry). Of these, 71% (n = 10) were pediatric cases (≤18 years) and half (n = 5) harbored the BRAF V600E mutation. As compared to the BRAF wild-type cohort (WT), the BRAF V600E cohort had a similar mean age at diagnosis [BRAF V600E: 7 years (3-12 y), vs. WT: 7.6 years (1-18 y)] but demonstrated a stronger male/female ratio (BRAF V600E: 4 vs WT: 0.67), and had both more multifocal CNS disease ( BRAFV600E: 80% vs WT: 20%) and systemic disease (BRAF V600E: 40% vs WT: none). Radiographic features of CNS-JXG varied but typically included enhancing CNS mass lesion(s) with associated white matter changes in a subset of BRAF V600E neoplasms. After clinical-radiographic correlation, pediatric ECD was diagnosed in the BRAF V600E cohort. Treatment options varied, including surgical resection, chemotherapy, and targeted therapy with BRAF-inhibitor dabrafenib in one mutated case. BRAF V600E CNS-JXG neoplasms appear associated with male gender and aggressive disease presentation including pediatric ECD. We propose a revised diagnostic algorithm for CNS-JXG that includes an initial morphologic diagnosis with a final integrated diagnosis after clinical-radiographic and molecular correlation, in order to identify cases of pediatric ECD. Future studies with long-term follow-up are required to determine if pediatric BRAF V600E positive CNS-JXG neoplasms are a distinct entity in the L-group histiocytosis category or represent an expanded pediatric spectrum of ECD.

Cladribine treatment for Erdheim-Chester disease involving the central nervous system and concomitant polycythemia vera: A case report

Erdheim–Chester disease (ECD), a rare form of non-Langerhans cell histiocytosis, is characterized by the infiltration of foamy CD68⁺ and CD1a^- histiocytes into multiple organ systems. Central nervous system (CNS) involvement has recently been reported to be a poor prognostic factor when treating ECD with interferon alpha. We report the case of a 66-year-old Japanese patient with ECD involving the CNS who harbored the BRAF V600E mutation and also concomitantly developed polycythemia vera with the JAK2 V617F mutation. We confirmed 2-chlorodeoxyadenosine (cladribine) therapy to be effective for the patient in this case.

Hematopoietic origin of Langerhans cell histiocytosis and Erdheim-Chester disease in adults

Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD) are rare histiocytic disorders induced by somatic mutation of MAPK pathway genes. BRAFV600E 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, BRAFV600E allele-specific polymerase chain reaction was used to map the neoplastic clone in 20 adults with LCH, ECD, and HCL. BRAFV600E 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 BRAFV600E 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.

Erdheim-Chester disease with novel gene mutations discovered as an incidental finding in explanted liver of a patient with hepatitis C cirrhosis: A case report and literature review

Erdheim-Chester disease (ECD) is a rare form of non-Langerhans cell histiocytosis characterized by xanthogranulomatous infiltration of foamy histiocytes frequently involving bone and other organ systems. We herein report a unique case of ECD discovered incidentally in an explanted liver in a 65-year-old male with end-stage liver disease secondary to hepatitis C cirrhosis. Histological examination and immunohistochemical studies in the explanted liver revealed prominent foamy histiocytes that were CD68 positive, but CD1a and S100 negative. Mutational hotspot analysis of the explanted liver using a panel of 47 most common cancer-related genes performed by next generation sequencing (NGS) revealed likely somatic mutations in the PDGFRA, PTEN, and HNF1A genes, but no BRAF codon 600 mutations were detected. The bone marrow showed similar findings as in the liver. Whole body PET and bone scans demonstrated increased heterogeneous uptake in bilateral humeral and femoral diaphysis, most compatible with ECD. To our knowledge, this is the first case report of ECD that involves mainly bone marrow and liver with novel genomic alterations. Our case highlights the diversity and complexity of this disease entity and the importance of multi-modality approach integrating clinical and radiologic features with histopathologic and molecular/genomic findings.

[Erdheim-Chester disease (ECD), an inflammatory myeloid neoplasia]

In a compatible clinico-radiological setting, the diagnosis of Erdheim-Chester disease (ECD) involves the analysis of histiocytes in tissue biopsies: they are typically foamy and CD68+ CD1a, whereas in Langerhans cell histiocytosis (LCH) they are CD68+ CD1a+. Overlap forms of histiocytoses are frequent. Technetium bone scintigraphy showing nearly constant tracer uptake by the long bones is highly suggestive of ECD and a 'hairy kidney' appearance on abdominal CT scan is observed in more than half ECD cases. CNS involvement is a strong prognostic factor and an independent predictor of death in cases of ECD. Optimal initial therapy for ECD appears to be administration of IFN-α (and/or pegylated IFN-α) and prolonged treatment significantly improves survival; however, tolerance may be poor. Best alternative therapies are anakinra, mainly effective for mild forms of the disease, infliximab, and sirolimus. Cases of ECD present with strong systemic immune activation, involving IFN-α, IL-1/IL1-RA, IL-6, IL-12, and MCP-1, consistent with the systemic immune Th-1-oriented disturbance associated with the disease. Between 57 and 75 % of ECD patients carry the BRAF^V600E mutation, an activating mutation of the proto-oncogene BRAF. More than 50 cases harboring BRAF mutation and with severe multisystemic and refractory ECD (sometimes associated with LCH) have been treated worldwide with vemurafenib, a BRAF inhibitor that proved to be very beneficial. Other recurrent mutations of the MAPK (NRAS, MAP2K1) and PIK3 pathways (PIK3CA) have been found among ECD patients. As recurrent mutations in the MAPK pathway are found in ECD and LCH on a background of chronic inflammation, we believe that both conditions should be redefined as an inflammatory myeloid neoplasia.

Biological and clinical significance of somatic mutations in Langerhans cell histiocytosis and related histiocytic neoplastic disorders

Langerhans cell histiocytosis (LCH), juvenile xanthogranuloma (JXG), and Erdheim-Chester disease (ECD) represent histiocytic disorders with a wide range of clinical manifestations. Until recently, mechanisms of pathogenesis have been speculative and debate has focused on classification of these conditions as reactive versus neoplastic. Genomic studies have been challenged by scarce tissue specimens, as well as heterogeneous nature of the lesions with variable infiltration of pathologic histiocytes. Whole-exome sequencing recently revealed a very low frequency of somatic mutations in LCH, JXG, and ECD compared to other neoplastic disorders. However, at least in the cases of LCH and ECD, there is a very high frequency of activating mutations in MAPK pathway genes, most notably BRAF-V600E, as well as MAP2K1, in LCH and NRAS in ECD. In ECD, recurrent mutations in the PI3K pathway gene PIK3CA have also been described. The heterogeneous clinical manifestations of these disorders may therefore be the cumulative result of activation of MAPK mutations (along with modifying signals from other pathways) at distinct stages of myeloid differentiation. Implications of this model include redefinition of LCH, JXG, and ECD as a group of clinically diverse myeloid neoplastic disorders with a common mechanism of pathogenesis. This model supports refocusing therapeutic strategies for these diseases on a personalized approach based on specific mutations and the cell(s) of origin.

[Clinical and pathologic characteristics of Erdheim-Chester disease]

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.

Recurrent RAS and PIK3CA mutations in Erdheim-Chester disease

Erdheim-Chester disease (ECD) is a rare histiocytic disorder that is challenging to diagnose and treat. We performed molecular analysis of BRAF in the largest cohort of ECD patients studied to date followed by N/KRAS, PIK3CA, and AKT1 mutational analysis in BRAF wild-type patients. Forty-six of 80 (57.5%) of patients were BRAFV600E-mutant. NRAS mutations were detected in 3 of 17 ECD BRAFV600E wild-type patients. PIK3CA mutations (p.E542K, p.E545K, p.A1046T, and p.H1047R) were detected in 7 of 55 patients, 4 of whom also had BRAF mutations. Mutant NRAS was present in peripheral blood CD14(+) cells, but not lymphoid cells, from an NRASQ61R mutant patient. Our results underscore the central role of RAS-RAF-MEK-ERK activation in ECD and identify an important role of activation of RAS-PI3K-AKT signaling in ECD. These results provide a rationale for targeting mutant RAS or PI3K/AKT/mTOR signaling in the subset of ECD patients with NRAS or PIK3CA mutations.

[Erdheim-Chester disease]

Erdheim-Chester disease is an orphan condition which involves the ongoing proliferation, migration and infiltration of the typical CD68(+), CD1a(-) histiocytes to various target foci. Consequently, both the infiltrating and fibrosing elements of the disease promote end organ damage and ultimately, failure. Presentation of the Erdheim-Chester disease typically involves longstanding diabetes insipidus in conjunction with intensifying bone pain that classically affects the femurs and tibiae. Alternatively, the disease may present with neurological deterioration of cerebellar nature. Thus, a high index of clinical suspicion is required when facing a patient with the combination of longstanding diabetes insipidus in conjunction with bone pain or cerebellar dysfunction. Typical symmetric, bilateral increased tracer uptake on a 99mTc bone scintigraphy invoLving the femurs and tibiae, is strongly suggestive of the Erdheim-Chester disease. interferon alpha is considered as the first line of treatment. Nevertheless, recent accumulated data suggests that this disease heavily relies on the Ras/Raf/MEK/ERK signal transduction pathway as inhibition of the V600E mutant BRAF by the small molecule vemurafenib among patients who are carriers of this mutation, yielded dramatic clinical responses.

Biological and therapeutic implications of the BRAF pathway in histiocytic disorders

Langerhans cell histiocytosis (LCH) has historically evolved in its classification from a primary immune dysregulatory disorder to what current evidence supports as a dendritic cell neoplasm with an immune-inflammatory component. A key part of the classification of LCH as a neoplasm has been the identification of BRAF V600E mutations in 35% to 60% of cases. Tumor protein p53 (TP53) and RAS mutations have also been identified, albeit in less than 2% of reported cases. Of note, over 50% of patients with another dendritic cell disease, Erdheim-Chester Disease, have also been shown to have BRAF V600E mutations. Although the BRAF mutations have not been shown to be associated with extent of disease, they may still provide a target for a molecularly guided approach to therapy. In cases of LCH in which no BRAF mutations were identified, there was evidence for activation of the RAS-RAF-MEK-extracellular signal-regulated kinases (ERK) pathway, suggesting that similar to other tumors, this pathway may be therapeutically exploitable. Anecdotal responses have been reported in a few patients with LCH and Erdheim-Chester Disease to vemurafenib, a BRAF V600E inhibitor. Although these results pave the way for careful, prospective clinical testing, selection of the optimal groups in which to test such inhibitors, alone or in combination, will be critical based on the toxicity profile thus far observed in adults with melanoma and other BRAF mutated tumors.

Dramatic efficacy of vemurafenib in both multisystemic and refractory Erdheim-Chester disease and Langerhans cell histiocytosis harboring the BRAF V600E mutation

Histiocytoses are rare disorders of unknown origin with highly heterogeneous prognosis. BRAFV600E gain-of-function mutations have been observed in 57% of cases of Langerhans cell histiocytosis (LCH) and 54% of cases of Erdheim-Chester disease (ECD), but not in other types of histiocytoses. Targeted therapy with an inhibitor of mutated BRAF (vemurafenib) improves survival of patients with melanoma. Here, we report vemurafenib treatment of 3 patients with multisystemic and refractory ECD carrying the BRAFV600E mutation; 2 also had skin or lymph node LCH involvement. The patients were assessed clinically, biologically (CRP values), histologically (skin biopsy), and morphologically (positron emission tomography [PET], computed tomography and magnetic resonance imaging). For all patients, vemurafenib treatment led to substantial and rapid clinical and biologic improvement, and the tumor response was confirmed by PET, computed tomography, and/or magnetic resonance imaging 1 month after treatment initiation. For the first patient treated, the PET response increased between months 1 and 4 of treatment. The treatment remained effective after 4 months of follow-up although persistent disease activity was still observed. Treatment with vemurafenib, a newly approved BRAF inhibitor, should be considered for patients with severe and refractory BRAFV600E histiocytoses, particularly when the disease is life-threatening.

Erdheim-Chester disease: report of a case with PCR-based analysis of the expression of osteopontin and survivin in Xanthogranulomas following glucocorticoid treatment

Erdheim-Chester disease (ECD) is a form of non-Langerhans histiocytosis. In this report, we show a case of ECD presenting diabetes insipidus and multiple xanthogranulomas received glucocorticoid treatment over a year. During this period, xanthogranulomas improved in response to the glucocorticoid therapy. Furthermore, the expression of osteopontin in xanthogranulomatous tissues significantly decreased following the treatment. Our data show the expression of osteopontin in xanthogranulomatous tissues of ECD. Furthermore, the osteopontin mRNA decreased following glucocorticoid therapy with xanthogranuloma regression, suggesting that the expression level of osteopontin could be a marker of the disease activity of ECD.

Clonal Cytogenetic Abnormalities in Erdheim-Chester Disease

Erdheim-Chester disease (ECD) is a rare histiocytic disorder of unknown etiology that involves predominantly bone and viscera. Whether ECD represents a reactive or neoplastic process has been debated since its initial description. Herein, we report for the first time the cytogenetic findings of a case of ECD diagnosed at Mayo Clinic Rochester. The tumor occurred in the right tibia of a 35-year-old man and showed the balanced chromosomal translocation t(12;15;20)(q11;q24;p13.3), among other numeric chromosomal abnormalities. The lesion was positive for CD68 and negative for CD1a and S100. These findings support the idea that some cases of ECD are clonal neoplastic disorders of putative histiocytic differentiation. However, additional studies are warranted to confirm whether the chromosomal abnormalities found in this case represent recurrent cytogenetic events.

[Erdheim-Chester disease: a non-Langerhans cell histiocytosis. A clinical-case and review of the literature]

We make a retrospective evaluation of clinical and radiologic features, treatment, and outcome of Erdheim-Chester disease, a rare non-Langerhans cell histiocytosis. We report a case of Erdheim-Chester disease and review 60 cases from the literature. These cases are consider to have Erdheim-Chester disease when they have either typical bone radiographs (symmetrical long bones osteosclerosis) and/or histologic criteria disclosing histiocytic infiltration with distinctive immunohistochemical phenotype of the non-Langerhans cell histiocytes with positive staining for CD68 and negative staining for S-100 protein and CD1a. Our patient undergoes chemiotherapy according to the LCH-II stratification and therapy plan (Vinblastine, Etoposide and Prednisone) and thereafter receives Carboplatin and Etoposide, and Somatostatin. She is alive and clinically well 33 months after onset of symptoms and the lesions don't appear to progress at imaging examinations. In conclusion, Erdheim-Chester disease may be confused with Langerhans cell histiocytosis as it sometimes shares the same clinical (exophthalmos, diabetes insipidus) or radiologic (osteolytic lesions) findings. However, the characteristics radiological pattern of Erdheim-Chester disease together the immunohistochemical phenotype of hystiocytic infiltration supports the theory that Erdheim-Chester disease is a unique disease entity distinct.