Intracellular and extracellular rhomboid shaped crystalline inclusions in a case of IgG lambda restricted plasma cell myeloma: a case report and review of the literature

Abstract

The presence of crystalline inclusions in plasma cell myeloma is a rare phenomenon and cases have been reported with rod, needle, and rectangular shaped crystals. Here, we present a case of IgG lambda restricted plasma cell myeloma with rhomboid shaped intracellular crystalline inclusions and extracellular crystal depositions in the bone marrow. Since rhomboid crystal depositions can be seen in other clinical conditions such as pseudogout, this case invites consideration of plasma cell myeloma in the differential diagnosis of patients with rhomboid crystalline deposition in the bone marrow and in sites/organs other than the bone marrow.

Figure 1

Plasma cell myeloma with intracytoplasmic and extracellular rhomboid crystalline inclusions. (a and b) Bone marrow aspirate stained with Wright-Giemsa. Note abundant rhomboid crystals present in the extracellular space (a; arrows) and intracytoplasmic in plasma cells (b; arrow-heads). (c) H&E stain of bone marrow biopsy section showing prominent rhomboid crystals (arrow). (d) Immunohistochemistry for lambda-chain highlights monotypic plasma cells with positive stain of the extracellular crystals (arrow). Bar 200 μm (a), 20 μm (b), and 50 μm (c and d).