A family is described which has exhibited in four generations a bizarre form of arthritis mutilans and osteolysis, the features of which seem to fit most closely with a diagnosis of hereditary multicentric osteolysis, a subgroup of idiopathic multicentric osteolysis. The differential diagnosis of arthritis mutilans associated with osteolysis is discussed; this includes a wide variety of disorders ranging from rheumatoid arthritis to rare conditions such as the Winchester syndrome.