Multiple myeloma in three siblings.

All three siblings of a family developed multiple myeloma. Two siblings had a history of monoclonal gammopathy; in one of these two siblings and in the third sibling, the disease progressed rapidly. A review of the literature shows that of 38 previously reported pairs of siblings with plasma cell disorders, eight families had a third affected sibling and four another affected relative. This clinical clustering suggests that some cases of multiple myeloma may have a hereditary basis and that other family members may be at risk for developing the disease.