Abstract
An 82-year-old male was admitted to our hospital because of anemia with Hb 6.9/dl. The serum monoclonal IgG of the κ type was detected. Bone marrow aspiration showed the presence of 38.9% atypical plasma cells with crystalline inclusions. These crystalline inclusions were stained with acid phosphatase, and remained unstained with MPO, PAS and Congo-Red staining. Immunofluorescence studies showed the plasma cells were positive for IgG-κ type immunoglobulin and CD138. Electron microscopy revealed varying numbers of stick-like, rod-shaped, rhomboid or rectangular crystals of a variety of lengths and sizes with a periodicity giving an appearance of longitudinal striation. The inclusions were most often surrounded by ribosomes. Some crystalline inclusions were located in the rough-surfaced endoplasmic reticulum. Their presence was probably due to an abnormality in the synthesis and/or secretion of immunoglobulin.
