[Focal lipodystrophy in the bone marrow].

Small areas of slowly progressive disseminated osteolytic disease of unknown clinical, radiological and biochemical aertiology developed over three years in a 59-year-old man with exercise-induced pain in the left leg as the only symptom. Several bone biopsies merely revealed circumscribed primary dystrophy of the univacuolar medullary fat tissue with destruction and new formation of bone. The process, which is restricted to fat tissue of the bone marrow, has been termed "focal liposystrophy". It was also found in a briefly described second case. The pathogenesis is largely identical with comparable changes in extra-osseous fatty tissue which are also of unknown aetiology and usually termed "idiopathic".