Erdheim-chester disease involving the bone marrow: A discussion of non-langerhans histiocytic disorders

Bone marrow involvement by a histiocytic lesion may result in a broad differential diagnosis. Erdheim-Chester disease is a rare aggressive histiocytic proliferation with systemic involvement that frequently causes bone lesions with a characteristic radiographic and clinical presentation. Most patients have bilateral and symmetric sclerotic bone lesions especially involving the long bones of the lower limbs. Extraskeletal involvement of the hypothalamus/ posterior pituitary, central nervous system, orbit, retroperitoneum, skin, lung, kidney, and heart can be seen in half of the cases. Here we report a case of Erdheim-Chester disease, and the clinicopathologic features and the differential diagnosis are discussed. The presented example illustrates the importance of a systematic approach in the evaluation of bone marrow histiocytic lesions.