Erdheim–Chester disease and Schnitzler syndrome: so near, and yet so far

Excerpt

A 56-year-old male presented with diabetes insipidus, non-infectious fever, night sweats, and pain in both lower legs and pelvis. Developing gradually over a period of 9 years, these symptoms were accompanied by increased acute phase markers (C-reactive protein = 63 mg/L, erythrocyte sedimentation rate = 52 mm/h and 72 mm/2 h, fibrinogen = 6.5 g/L). Technetium-99m pyrophosphate bone scintigraphy showed abnormal tracer uptake predominantly in the long bones of the lower extremities, with additional hot spots in the skull, right shoulder, left humerus, and both radial bones (Fig. 1). Positron emission tomography (PET) identified a similar pattern of 18F-fluorodeoxyglucose uptake correlating with osteosclerotic lesions on conventional radiography (X-ray) and computed tomography (CT). Subsequently, histological findings of CD68- and S100-positive, CD1a-negative foamy histiocytes from a bone biopsy were compatible with Erdheim–Chester disease. Moreover, the obtained tissue samples were positive for BRAF V600E mutation on CE-IVD validated BRAF 600/601 StripAssay (ViennaLab Diagnostics GmbH, Austria) (Fig. 2).

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