IgD myeloma with intracytoplasmic crystalline inclusions.

Plasma cells from an IgD myeloma contained intracytoplasmic crystals. By electron microscopy, these crystals had 13-nm periodicity and were contained within vacuoles formed of smooth membranes. Immunofluorescence microscopy of the neoplastic plasma cells demonstrated diffuse cytoplasmic staining with accentuated Golgi region staining specific for immunoglobulin delta heavy and lambda light chains. The observations support an association between the crystal-containing vacuoles and the Golgi apparatus. Previously reported plasma cell and lymphocyte crystalline inclusions are reviewed, and compared with the crystals described in this report.