Synonyms

• ECD
• histiocytosis X variant

Category

Syndrome

Behaviour

Benign

Gender

Male

Epidemiology

• Rare histiocytic storage disorder
• Peak incidence in middle-aged adults
• Multisystem involvement common

Clinical Features

• Bone pain from osteosclerosis
• Dyspnoea if pulmonary involvement
• CardioVascular symptoms
• Constitutional symptoms

Location

• Femur and tibia most common (bilateral symmetric osteosclerosis)
• Lungs
• Mediastinum
• Retroperitoneum
• CNS

Imaging

• Plain radiograph: bilateral symmetric long Bone osteosclerosis
• CT chest: mediastinal, pericardial, or pulmonary involvement
• MRI: assess extent

Pathology

• Foamy histiocytes (lipid-laden macrophages)
• CD68+, S100 Variable
• Cholesterol crystal deposition

Genetics

• BRAF V600E mutations in 50%
• MAPK pathway alterations

Treatment

• BRAF inhibitors (vemurafenib) if BRAF-mutant
• IFN-alpha in some cases
• Observation if indolent

Prognosis

• Variable - depends on organ involvement
• Poor if cardiac/CNS involvement
• BRAF inhibitors improved outcomes

Key Points

• Bilateral symmetric femoral/tibial osteosclerosis is characteristic
• BRAF V600E testing important for targeted therapy
• Multisystem involvement common

Workup - Blood Tests

• FBC, U&E, LFTs - baseline
• Lipid profile

Workup - Local Imaging

Plain radiograph: bilateral symmetrical osteosclerosis

Workup - Biopsy

• Bone or tissue biopsy - confirm diagnosis
• BRAF V600E mutation testing

Workup - Staging

• CT chest/abdomen/pelvis - assess multisystem involvement
• MRI brain - if neurological symptoms

Workup - Other

• BRAF testing for targeted therapy eligibility
• Multidisciplinary assessment given multisystem nature