IgD myeloma, which is particularly severe, accounts for only 1-3% of all myeloma cases, and the kappa subtype contributes only 10-30% of IgD myelomas. We report a new case.

Case-report. - A 59-year-old man was admitted for inflammatory low back pain with L5 sciatica and diffuse bone pain. The symptoms had been present for 3 months, during which he had experienced a severe decline in general health. Laboratory test abnormalities included an erythrocyte sedimentation rate of 70 mm/h, normochromic normocytic aplastic anemia, hypercalcemia (3.5 mmol/l), and serum creatinine elevation to 583 μmol/l. Tests were negative for cryoglobulinemia. Serum protein electrophoresis showed hypergammaglobulinemia but no monoclonal peak. Immunoelectrophoresis, however, detected a faint IgD kappa band in the blood and a homogeneous kappa band in the urine. Bone marrow aspirated from the sternum was found to contain 30% of malignant plasma cells. Biopsies for amyloidosis were negative. Radiographs disclosed multiple punched-out lesions with no evidence of spinal cord compression. Symptomatic treatment was given to correct the hypercalcemia, and combination chemotherapy was started.

Discussion. - IgD kappa myeloma is a severe variant of myeloma often associated with extraosseous lesions, renal failure, and amyloidosis. The monoclonal component is absent or faint by serum protein electrophoresis, making the diagnosis difficult. The pathogenesis is unclear and the prognosis grim.