Multiple myeloma with acicular crystalline inclusion bodies

A 41-year-old female patient was admitted to our endocrinology department with the symptoms of worsening malaise, difficulty in walking and numbness in her limbs. Blood tests revealed a red blood cell count of 3.11 × 1012/L, haemoglobin level of 97 g/L, urinary Igκ at 1.11 g/L, Igλ at 0.05 g/L, resulting in a κ/λ ratio of 22.20. Additional findings included urinary beta-microglobulin levels exceeding 2500 μg/L, urinary immunoglobulin at 23 mg/L, urinary albumin levels above 50 mg/L and serum beta-microglobulin at 5.36 μg/L. Bone marrow aspiration showed that 9% of the total cells were plasma cells, with 7% containing acicular crystalline inclusion bodies. These plasma cells varied in size, exhibited abundant cytoplasm and displayed eccentrically located nuclei. Some cells were binucleated, with the cytoplasm containing varying numbers of acicular crystalline inclusion bodies (Wright staining, 100× objective; images, upper left, middle, and right panels). Flow cytometry analysis revealed that 3.61% of the aberrant monoclonal plasma cells expressed CD45, CD38, CD138, CD81, CD117, CD27 and CD28dim, with kappa light chain restriction (images, lower left, middle and right panels). Based on these findings, a diagnosis of multiple myeloma, kappa light chain type, was established. The presence of crystalline immunoglobulin inclusions in this case is an uncommon occurrence. The presence of crystalline inclusions of immunoglobulin in this case is a rare finding. Crystallisation is thought to occur on the surface of the rough endoplasmic reticulum, where the biochemical properties of the particular monoclonal protein produced in that case of myeloma favour its condensation into a crystal structure (Miyoshi I, Daibata M, Saito T, Ohtsuki Y, Taguchi H. Bence Jones myeloma cells with crystalline inclusions. Intern Med 2006;45(5):337–8). This study is supported by the Scientific and Technological Research Program of Chongqing Municipal Education Commission (KJQN202000443). Ethical review and approval were waived for this study due to the retrospective description of a few cases without identifiable patient data. Consent for publication, both in print and electronically, has been obtained from the patient.