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Erdheim-Chester disease
Erdheim-Chester disease
Clinical features Erdheim-Chester disease (ECD) is a rare, but increasingly recognized, histiocytosis. Until recently, ECD was considered a non-Langerhans cell histiocytosis and classified as a subset of xanthogranulomatosis, but in the light of more recent molecular findings is now thought to be better grouped along with Langerhans cell histiocytosis.1,2 Most cases are diagnosed between the ages of 40 and 70 years, and there is possibly a male predominance.3,4 The diagnosis is made by identifying characteristic histologic and radiological findings in the appropriate clinical context. Bone scan or PET scan typically demonstrate symmetrical diaphyseal and metaphyseal osteosclerosis in the legs, particularly the distal ends of the femur and proximal tibia.5
Biopsy of lesional tissue reveals numerous lipid-laden foamy histiocytes in a variably fibrotic background. Multinucleate and Touton-type giant cells may also be present.3 In the skin, this process tends to extend into the deeper reticular dermis, unlike classic xanthelasma, and fibrosis may be less marked.3 The histiocytes express CD68, CD163, and, variably, FXIIIA, but are negative for CD1a, S100 and langerin.3,5 In a proportion of cases, there may also be a component of Langerhans cell histiocytosis in the lesional tissue.3,28
Infiltration of nearly every organ system has been reported in ECD, but the most commonly affected tissues are bone, large vessels, heart, retroperitoneum, orbit, lung, CNS, and endocrine system.4โ11
Skin is involved in 20โ32% of cases.4,12,13 The most frequent manifestation is the presence of xanthelasma, usually in the form of yellowish plaques
Differential diagnosis The pathological features are indistinguishable from those of juvenile xanthogranuloma (JXG)/xanthogranulomatous histiocytosis. Accurate diagnosis is therefore dependent on careful clinical pathological correlation and adherence to consensus guidelines, although demonstration of a BRAF mutation may also be helpful.2 The histiocytes in ECD are morphologically and phenotypically different from those seen in Langerhans cell histiocytosis, the latter expression CD1a, S100 and langerin.