Consensus guidelines for the diagnosis and clinical management of Erdheim-Chester disease

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.

A rare presentation of Erdheim Chester disease in a pediatric patient subsequently cured on the LCH III protocol

Background

Erdheim Chester disease (ECD) is very rare in pediatrics with no standard treatment guidelines. Here we present the case of a pediatric ECD patient who was cured with a Langerhan cell histiocytosis (LCH) directed chemotherapy protocol.

Aim

The aim of the report was to publish this rare presentation of ECD in pediatrics and highlight the complete response obtained to treatment.

Methods

The details of the patient were extracted by a retrospective review of her clinical records.

Results (Case)

An 11 years old girl presented with fever and bone pain. On investigating she had multiple lytic bony lesions scattered throughout her skeleton. A biopsy from one of the bone lesions confirmed the diagnosis to be ECD. ECD is very rare in pediatrics and this case adds to the existing list of 11 previously reported ones. Also, worth mention is the fact that the child presented with isolated skeletal involvement in form of multiple osteolytic lesions. The child was started on the LCH‐III protocol on which she achieved a cure.

Conclusion

Lytic bone lesions in a child may be present in ECD. A subset of ECD may have good response to LCH like chemotherapy.

Prevalence of Hypothyroidism in Patients With Erdheim-Chester Disease

IMPORTANCE

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis affecting multiple organs and commonly caused by somatic pathogenic variants in BRAF V600E and mitogen-activated protein kinase genes. Clinical features of ECD result from histiocytic involvement of various tissues; while endocrine involvement in ECD occurs frequently, the prevalence of central or primary hypothyroidism has not been thoroughly investigated.

OBJECTIVE

To assess hypothalamus-pituitary-thyroid (HPT) dysfunction in patients with ECD.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study included 61 patients with ECD who were enrolled in a natural history study at a tertiary care center between January 2011 and December 2018. ECD was diagnosed on the basis of clinical, genetic, and histopathological features. Data were analyzed in March 2020.

EXPOSURE

Diagnosis of ECD.

MAIN OUTCOMES AND MEASURES

Main outcome was the prevalence of thyroid dysfunction in adults with ECD compared with community estimates. Patients underwent baseline evaluation with a thyroid function test, including thyrotropin, free thyroxine (fT4), and total thyroxine (T4), and sellar imaging with magnetic resonance imaging or computed tomography scan. The association of HPT dysfunction was assessed for differences in age, sex, body mass index, BRAF V600E status, high sensitivity C-reactive protein level, sellar imaging, and pituitary hormonal dysfunction.

RESULTS

A total of 61 patients with ECD (46 [75%] men; mean [SD] age, 54.3 [10.9] years) were evaluated. Seventeen patients (28%) had hypothyroidism requiring levothyroxine therapy. The prevalence of both central and primary hypothyroidism were higher than community estimates (central hypothyroidism: 9.8% vs 0.1%; odds ratio, 109.0; 95% CI, 37.4-260.6; P < .001; primary hypothyroidism: 18.0% vs 4.7%; OR, 4.4; 95% CI, 2.1-8.7; P < .001). Patients with hypothyroidism (both primary and central), compared with patients with euthyroidism, had higher body mass index (median [interquartile range] 31.4 [28.3-38.3] vs 26.7 [24.4-31.9]; P = .004) and a higher prevalence of panhypopituitarism (7 [47%] vs 3 [7%]; P < .001). Among patients with hypothyroidism, those with central hypothyroidism, compared with patients with primary hypothyroidism, had a lower mean (SD) body mass index (28.3 [2.6] vs 36.3 [5.9]; P = .007) and higher frequencies of abnormal sellar imaging (5 [83%] vs 3 [27%]; P = .050) and panhypopituitarism (5 [83%] vs 3 [27%]; P = .050).

CONCLUSIONS AND RELEVANCE

In this cohort study, a higher prevalence of central and primary hypothyroidism was identified in patients with ECD compared with the community. There should be a low threshold for testing for hypothyroidism in patients with ECD, and treatment should follow standard guidelines.

Central nervous system involvement in Erdheim-Chester disease: An observational cohort study

OBJECTIVE

CNS involvement in Erdheim-Chester disease (ECD) leads to substantial morbidity and mortality. To assess CNS manifestations in a French cohort of 253 patients with ECD, we determined clinical characteristics and outcomes, including those under targeted therapies.

METHODS

This was a retrospective longitudinal study. CNS manifestations were determined by clinical examination and brain or spine MRI. Targeted therapy efficacy was assessed using global assessment from a physician and a radiologist. The study was approved by the ethics committee Comité de Protection des Personnes Ile de France III.

RESULTS

Ninety-seven of 253 patients (38%) with ECD had CNS involvement. CNS involvement was significantly associated with a younger age at diagnosis (mean 55.5 years) and at symptom onset (mean 50.5 years), as well as with the presence of the BRAF ^V600E mutation (in 77% of cases), xanthelasma (34%), and diabetes insipidus (36%). Median survival among patients with CNS involvement was significantly lower than that of patients with ECD without CNS involvement (124 months vs 146 months, p = 0.03). Seventy-four CNS MRIs were centrally reviewed, which showed 3 patterns: tumoral in 66%, pseudo-degenerative in 50%, and vascular in 18%. Targeted therapy (BRAF or MEK inhibitors) was associated with improved symptoms in 43% of patients and MRI improvement in 45%.

CONCLUSIONS

CNS manifestations are typically associated with poor prognosis in patients with ECD. Three distinct patterns can be recognized: tumoral, pseudodegenerative, and vascular.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that targeted therapy leads to clinical or imaging improvement in almost 50% of patients.

Ultra-rare cystic disease

Diffuse cystic lung diseases include a group of heterogeneous disorders characterised by the presence of cysts within the lung parenchyma, sometimes showing a characteristic computed tomography scan pattern that allows diagnosis. The pathogenetic mechanisms underlying cyst formation in the lung are still not clear and a number of hypotheses have been postulated according to the different aetiologies: ball-valve effect, ischaemic dilatation of small airways and alveoli related to infiltration and obstruction of small vessels and capillaries that supply the terminal bronchioles and connective tissue degradation by matrix metalloproteases. A wide number of lung cyst diseases have been classified into six diagnostic groups according to the aetiology: neoplastic, congenital/genetic, lymphoproliferative, infective, associated with interstitial lung diseases, and other causes. This article focuses on lymphangioleiomyomatosis, pulmonary Langerhans cell histiocytosis and Erdheim–Chester disease, Birt–Hogg–Dubé, follicular bronchiolitis and lymphocytic interstitial pneumonia, light-chain deposition disease and amyloidosis, congenital lung disease associated with aberrant lung development and growth, and cystic lung disease associated with neoplastic lesion. These cystic diseases are epidemiologically considered as ultra-rare conditions as they affect fewer than one individual per 50 000 or fewer than 20 individuals per million. Despite the rarity of this group of disorders, the increasing use of high-resolution computed tomography has improved the diagnostic yield, even in asymptomatic patients allowing prompt and correct therapy and management without the need for a biopsy.

Diffuse cystic lung diseases show a characteristic CT scan pattern that often allows for diagnosis, even in asymptomatic patients, allowing prompt correct therapy and management without the needing of a biopsyhttps://bit.ly/2wIUKet

Bronchoalveolar lavage as a diagnostic procedure: a review of known cellular and molecular findings in various lung diseases

Bronchoalveolar lavage (BAL) is a commonly used procedure in the evaluation of lung disease as it allows for sampling of the lower respiratory tract. In many circumstances, BAL differential cell counts have been reported to be typical of specific lung disorders. In addition, more specific diagnostic tests including molecular assays such as polymerase chain reaction (PCR) or enzyme-linked immunosorbent assay, special cytopathologic stains, or particular microscopic findings have been described as part of BAL fluid analysis. This review focuses on common cellular and molecular findings of BAL in a wide range of lung diseases. Since the performance of the first lung irrigation in 1927, BAL has become a common and important diagnostic tool. While some pulmonary disorders have a highly characteristic signature of BAL findings, BAL results alone often lack specificity and require interpretation along with other clinical and radiographic details. Development of new diagnostic assays is certain to reinforce the utility of BAL in the future. Our review of the BAL literature is intended to serve as a resource to assist clinicians in the care of patients with lung disorders.

[Erdheim-Chester disease presenting with bilateral orbital involvement: Report of three cases]

PURPOSE

To report treatment outcomes of orbital tumors associated with Erdheim-Chester disease and to highlight the importance of systemic work-up in patients presenting with bilateral proptosis.

PATIENTS AND METHODS

Three patients with Erdheim-Chester disease, whose initial manifestation was bilateral proptosis, were retrospectively studied. The course of onset, clinical, imaging and histopathological features, systemic associations and response to treatment were reviewed. The main outcome measures were Hertel measurements and orbital tumor regression on imaging studies.

RESULTS

All patients presented with bilateral non-pulsatile proptosis resistant to retropulsion and headeache without specific localization. Magnetic resonance imaging studies showed bilateral intraconal orbital tumors. Incisional biopsy of these tumors demonstrated CD68+, CD1a-, and S100- histiocytic infiltrates consistent with the diagnosis of Erdheim-Chester disease. The BRAFV600E mutation was found in all cases. Systemic work-up revealed asymptomatic bony involvement in the lower extremities, perirenal fibrosis, central nervous system and cardiac involvement. All patients initially received pegylated interferon-α2a, which resulted in excellent responses except for the orbital tumors. Two patients were then treated with vemurafenib, which resulted in rapid regression of the orbital lesions.

CONCLUSION

Pegylated interferon-α was highly effective in the control of cardiac, perirenal, skeletal and cerebral involvement but not the orbital tumors. The infiltrative orbital lesions of Erdheim-Chester disease would appear more responsive to vemurafenib.

Solitary juvenile xanthogranuloma of the hypopharynx. Clinico-pathologic study in a child with β-Thalassemia Major and Cutaneous Mastocytosis

Juvenile Xanthogranuloma (JXG), the most common pediatric non-Langerhans cell histiocytosis, may rarely occur in association with Neurofibromatosis (types 1 and 2), Juvenile Myelomonocytic Leukemia and Cutaneous Mastocytosis (CM) and, morphologically, mimics Erdheim-Chester Disease tissue lesions and ALK-positive histiocytosis. We describe a 4-year-old girl with Beta-Thalassemia Major who developed an hypopharyngeal BRAFV600E- and ALK-negative JXG and CM. JXG has been rarely reported in the aerodigestive tract and in association with CM. In this molecular era, knowledge of genetic heterogeneity of JXG and clinical scenarios in which it may develop is essential for the appropriate diagnosis and treatment of each individual patient.

A scale for patient-reported symptom assessment for patients with Erdheim-Chester disease

Erdheim-Chester disease (ECD) is an ultra-rare hematologic neoplasm characterized by somatic mutations of the MAPK pathway and by accumulation of lesional histiocytes within tissues. Clinical phenotypes and sites of disease involvement are heterogenous in ECD, and no tool exists for systematic and comprehensive assessment of ECD symptomatology. We describe a collaborative effort among ECD specialists, patient-reported outcome (PRO) methodologists, and ECD patients to develop the Erdheim-Chester Disease Symptom Scale (ECD-SS): a symptom inventory for clinical ECD care and evaluation of ECD therapies. Methodologically rigorous focus groups led to the identification of 63 ECD symptoms in 6 categories, incorporated into the ECD-SS with respect to both severity and frequency. Among 50 ECD patients participating in a prospective registry study completing the ECD-SS, 46 (92%) reported neurological/psychological symptoms, 29 (58%) reported pain, and at least one-half reported mood symptoms, memory problems, or fatigue. Symptoms were highly frequent or almost constant regardless of their severity. The ECD-SS is a rigorously developed, patient-centered tool that demonstrates the wide and previously unappreciated burden of symptomatology experienced by ECD patients. Further studies will refine the symptom inventory and define its psychometric properties and role in clinical care and investigation in the context of ECD.

The Role of Amygdala in Self-Conscious Emotions in a Patient With Acquired Bilateral Damage

Shame plays a fundamental role in the regulation of our social behavior. One intriguing question is whether amygdala might play a role in processing this emotion. In the present single-case study, we tested a patient with acquired damage of bilateral amygdalae and surrounding areas as well as healthy controls on shame processing and other social cognitive tasks. Results revealed that the patient's subjective experience of shame, but not of guilt, was more reduced than in controls, only when social standards were violated, while it was not different than controls in case of moral violations. The impairment in discriminating between normal social situations and violations also emerged. Taken together, these findings suggest that the role of the amygdala in processing shame might reflect its relevance in resolving ambiguity and uncertainty, in order to correctly detect social violations and to generate shame feelings.

Neurologic and oncologic features of Erdheim-Chester disease: a 30-patient series

BACKGROUND

Erdheim-Chester disease (ECD) is a rare histiocytic neoplasm characterized by recurrent alterations in the MAPK (mitogen-activating protein kinase) pathway. The existing literature about the neuro-oncological spectrum of ECD is limited.

METHODS

We present retrospective clinical, radiographic, pathologic, molecular, and treatment data from 30 patients with ECD neurohistiocytic involvement treated at a tertiary center.

RESULTS

Median age was 52 years (range, 7-77), and 20 (67%) patients were male. Presenting symptoms included ataxia in 19 patients (63%), dysarthria in 14 (47%), diabetes insipidus in 12 (40%), cognitive impairment in 10 (33%), and bulbar affect in 9 (30%). Neurosurgical biopsy specimens in 8 patients demonstrated varied morphologic findings often uncharacteristic of typical ECD lesions. Molecular analysis revealed mutations in BRAF (18 patients), MAP2K1 (5), RAS isoforms (2), and 2 fusions involving BRAF and ALK. Conventional therapies (corticosteroids, immunosuppressants, interferon-alpha [IFN-α], cytotoxic chemotherapy) led to partial radiographic response in 8/40 patients (20%) by MRI with no complete responses, partial metabolic response in 4/16 (25%), and complete metabolic response in 1/16 (6%) by 18F-fluorodeoxyglucose (FDG)-PET scan. In comparison, targeted (kinase inhibitor) therapies yielded partial radiographic response in 10/27 (37%) and complete radiographic response in 14/27 (52%) by MRI, and partial metabolic response in 6/25 (24%) and complete metabolic response in 17/25 (68%) by FDG-PET scan.

CONCLUSIONS

These data highlight underrecognized symptomatology, heterogeneous neuropathology, and robust responses to targeted therapies across the mutational spectrum in ECD patients with neurological involvement, particularly when conventional therapies have failed.

Erdheim-Chester Disease: A Rare Clinical Entity

Pericardial effusion represents a diagnostic challenge. Erdheim-Chester disease (ECD), though a rare cause, should be considered in the differential diagnosis. An 88-year-old woman was admitted to the hospital due to retrosternal pain, dyspnoea and constitutional symptoms. Hypoxaemic respiratory failure and increased inflammatory markers were documented. A chest x-ray revealed an increased cardiothoracic ratio. An echocardiogram showed a moderate-volume pericardial effusion, without signs of cardiac tamponade. A thoraco-abdomino-pelvic CT scan found a bilateral perirenal soft tissue halo. Perirenal mass biopsy showed diffuse infiltration by foamy histiocytes (CD68+), without IgG4, compatible with ECD. The correlation of anamnesis, radiology and histology is crucial for the diagnosis of ECD.

LEARNING POINTS

Erdheim-Chester disease is a non-Langerhans cell histiocytosis that affects multiple organs and systems.Thorough study of a pericardial effusion is important as it is still considered idiopathic in 10-20% of cases.It is a rare disease so high diagnostic suspicion is important. The diagnosis is established through clinical manifestations, radiologic findings and histological confirmation.

Retroperitoneal Erdheim-Chester disease without skeletal bone involvement mimicking uterine sarcoma with multiple organ involvement

Erdheim-Chester disease (ECD) is a rare type of non-Langerhans cell histiocytosis and is characterized by the diffuse histiocytic infiltration of multiple organs. Retroperitoneal ECD, especially with uterine involvement, is extremely rare. We report about a 73-year-old woman who presented with vaginal spotting for a month and experienced abdominal pain along with pus-like urine. Computed tomography revealed an irregular mass-like lesion in the uterus, possibly a uterine sarcoma, invading the ureter, rectosigmoid, and bladder. A tissue biopsy of the retroperitoneal mass revealed typical morphological and immunohistochemical features of ECD. However, clinical features, especially long bone involvement, did not coincide with ECD, and BRAF V600E gene mutation was not detected. We made a diagnosis of atypical retroperitoneal ECD mimicking uterine sarcoma with multiple organ involvement.

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: A Case Report and Review of the Literature

Erdheim-Chester disease (ECD) is a rare form of non-Langerhans’ cell histiocytosis characterized by xanthogranulomatous infiltration of foamy histiocytes surrounded by fibrosis. ECD may be asymptomatic or present as a multi-systemic disease with life-threatening manifestations, most commonly involving the skeletal system. Immunohistochemical staining demonstrates cells that are CD68+, CD1a–, and S100– with an absence of Birbeck granules. We report a case of a 69-year old male patient who presented with neurological symptoms – eventually thought to be separate to his diagnosis of ECD. It represents the ability to diagnose ECD based just on radiological findings in an otherwise asymptomatic individual.

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 treated with IFN-α monitored using plasma and urine cell-free DNA

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.

Erdheim-Chester disease presenting with cough, abdominal pain, and headache

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytic disorder. The diagnosis was based on the relationship between radiologic findings, clinical manifestations, and pathologic features of the bone biopsy. We report a case of ECD with unusual presenting symptoms: a 56 year-old man presented with cough, abdominal pain, and recurrent episodes of headache associated without any seizures. Peculiar computer tomography (CT) findings were key for the diagnostic suspicion. Bone biopsy and other radiological investigations confirmed the diagnosis. CT findings can help raise the suspicion of ECD. CT is easy to perform and widely available in comparison with kinetic cardiac magnetic resonance imaging and nuclear imaging. Therefore, CT findings of ECD can reduce the therapeutic delay between diagnosis and therapy prescription.

Practical approach to vasculitides in adults: an overview of clinical conditions that can mimic vasculitides closely

Primary systemic vasculitides are rare diseases affecting blood vessel walls. The type and patterns of distribution of the organs affected usually reflect the size of the vessels predominantly involved, and the patterns of clinical manifestations are generally useful to reach a specific diagnosis. However, presenting symptoms may lack adequate specificity for a prompt diagnosis, leading to a diagnostic (and therapeutic) delay, often causing irreversible damage to the affected organs. Due to their rarity and variable clinical presentation, the diagnosis of primary vasculitides could be challenging for physicians. Vasculitis mimickers, i.e. the clinical conditions that could be likely mistaken for vasculitides, need to be carefully ruled out, especially before starting the immunosuppressive therapy. We present here a practical approach to the diagnosis of primary systemic vasculitides involving large, medium and small size vessels, and reviewed most of the conditions that could mimic primary systemic vasculitides.

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.

Aortitis and periaortitis: The puzzling spectrum of inflammatory aortic diseases

Aortitis and periaortitis are inflammatory diseases of the aorta and its main branches; they differ in the extension of inflammation, which is confined to the aortic wall in aortitis, and spreads to the periaortic space in periaortitis. Aortitis is classified as non-infectious or infectious. Non-infectious aortitis represents a common feature of large-vessel vasculitides but can also be isolated or associated with other rheumatologic conditions. Periaortitis can be idiopathic or secondary to a wide array of etiologies such as drugs, infections, malignancies, and other proliferative diseases. Notably, both aortitis and periaortitis may arise in the context of IgG4-related disease, a recently characterised fibro-inflammatory systemic disease. Prompt recognition, correct diagnosis and appropriate treatment are essential in order to avoid life-threatening complications.

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.

Unusual manifestations of diffuse-type tenosynovial giant cell tumor in two patients: importance of radiologic-pathologic correlation

Diffuse-type tenosynovial giant cell tumor (TSGCT) is a rare, locally aggressive neoplasm. It most commonly occurs in the knee, followed by the hip, and has distinctive imaging features, including mass-like foci of low T2 signal intensity, "blooming" on gradient-echo MRI, and pronounced uptake on FDG PET/CT. Histologically, TSGCT demonstrates a neoplastic population of mononuclear cells admixed with hemosiderin-laden macrophages, foamy histiocytes, inflammatory cells, and osteoclast-like giant cells. In cases where diffuse-type TSGCT presents in an uncommon location or with atypical features, the imaging diagnosis may be challenging. Furthermore, because of its polymorphous appearance, it may be mistaken microscopically for other neoplastic and non-neoplastic histiocytic lesions. Herein, we present two cases of diffuse-type TSGCT presenting as large masses, and underscore the importance of radiologic-pathologic correlation for accurate diagnosis.

Multimodal Chorioretinal Imaging in Erdheim-Chester Disease

Purpose

To analyze the subclinical intraocular involvement using multimodal imaging approach in patients affected by Erdheim-Chester disease (ECD) without ocular symptoms.

Patients and Methods

In this prospective cross-sectional study, 18 eyes of 9 consecutive patients with ECD were enrolled. Each patient underwent comprehensive ocular examination and extensive multimodal chorioretinal imaging.

Results

None of the patients presented any evidence of chorioretinal localization of disease using multimodal imaging. One patient exhibited a choroidal nevus complicated by active polypoidal choroidal neovascularization. Subretinal hyperreflective material was seen in three eyes, mainly resembling acquired vitelliform lesion. One patient had an isolated intraretinal hemorrhage. Most patients exhibited peripheral vascular abnormalities (ie, microaneurysms, peripheral vascular leakage). Fundus autofluorescence showed faint hyperautofluorescence in eleven eyes.

Conclusion

Intraocular involvement is an extremely rare event of an extremely rare disease. In patients affected by ECD without ocular symptoms, advance multimodal imaging examinations did not show signs of subclinical chorioretinal involvement related to the disease.

The unique burden of rare cancer caregiving: caregivers of patients with Erdheim-Chester disease

Research examining the experience of informal caregivers (ICs) for patients with rare cancers is limited. This was a mixed-methods pilot study of 14 ICs for patients with Erdheim-Chester disease (ECD), an ultra-rare neoplasm. Participants were predominantly female and over half provided at least 60% of their loved one's care. Participants completed measures of the impact of caregiving, caregiver burden, unmet needs, quality of life, anxiety, and depression. Participants reported substantial impact of caregiving, including limiting (50%) or discontinuing (21%) paid employment, and exhausting financial savings (43%). ICs reported a moderate level of burden with five (38%) reporting risk for burnout. While participants reported anxiety (64%) and depression (14%), their overall quality of life was favorable. Semi-structured interviews highlighted factors related to the distress and isolation of navigating a rare cancer. ECD ICs report burden and distress shaped by the experience of providing care for a patient with a rare cancer.

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.

Choreo-Athetosis and Ataxia as Leading Features in a Case of Erdheim-Chester Disease

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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.

Extranodal Rosai-Dorfman Disease Presenting as a Pericardial Mass and Constrictive Pericarditis

Rosai-Dorfman disease is a rare, idiopathic disorder of histiocyte proliferation. We describe a case of a 59-year-old woman who presented with heart failure symptoms from a large pericardial mass causing constrictive pericarditis. Pathologic findings including immunohistochemistry suggested the diagnosis. She was treated with corticosteroids and improved clinically. (Level of Difficulty: Advanced.)

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.

Vemurafenib as first-line therapy in BRAF-V600E-mutant Erdheim-Chester disease with CNS involvement

Erdheim-Chester disease (ECD) is a rare histiocytosis that may affect the central nervous system (CNS). Infiltration by the disease occurs throughout the neuroaxis, usually involving the dentate nucleus and the pons, manifested as a pyramido-cerebellar syndrome. CNS involvement is an adverse prognostic factor which warrants prompt evaluation and treatment. BRAF mutation occurs in more than half of the cases and has become central in the therapeutic approach. There is rapidly growing evidence that BRAF inhibitors such as vemurafenib or dabrafenib are effective in treating CNS-spread disease. We present a patient with BRAF-V600E-mutant ECD with a classical pyramido-ataxic onset of disease who improved after prompt diagnosis with vemurafenib treatment as first-line therapy.