Extranodal Rosai-Dorfman disease involving the bone marrow: a case report.

Sinus histiocytosis with massive lymphadenopathy (SHML), also known as Rosai-Dorfman disease, is a very rare disorder of unknown etiology. Although classical SHML usually presents as massive, painless, bilateral neck lymph node enlargement, approximately 25% to 40% of SHML cases described to date present in extranodal organs or tissues, such as skin, upper respiratory tract, and bone etc. However, bone marrow as a site of initial presentation by SHML has not been described since the disease was initially recognized in 1969. Here, we report the first case of bone marrow involvement by extranodal SHML, which occured in a 73 year-old man with a history of refractory idiopathic thrombocytopenia purpura. The bone marrow biopsy demonstrates the distinctive and characteristic morphologic and immunophenotypic features of extranodal SHML.