Unusual evolution of Waldenström's macroglobulinemia into osteolytic myeloma.

We report the unusual transformation of a case of Waldenström's macroglobulinemia (WM) into IgM multiple myeloma (MM). The initial clinical and biological presentation of the disease was typical smouldering WM, with lymphocytic infiltration of the bone marrow. Five years later, signs of transformation appeared: the patient presented with diffuse osteolytic bone lesions without organomegaly, and the bone marrow was infiltrated with characteristic malignant plasma cells.