Nonsecretory myeloma, immunoglobulin D myeloma, and plasma cell leukemia.

Nonsecretory myeloma, which accounts for 1% to 5% of all myelomas, is characterized by the absence of detectable M-protein in serum and urine. The presenting features of nonsecretory myeloma are similar to those in patients with a detectable M-protein, except for the absence of renal function impairment. The response to therapy and survival of patients with nonsecretory myeloma are similar to those of patients with measurable M-protein. Immunoglobulin D myeloma represents 2% of all myelomas. Patients with IgD myeloma usually present with a small band or no evident M-spike on serum electrophoresis and heavy light-chain proteinuria. Thus, IgD myeloma can be considered a variant of Bence Jones myeloma; the presence of the IgD M-protein and the predominance of the lambda light chain are the only distinctive features. The median survival of patients with IgD myeloma is almost 2 years, with one fifth of them surviving for more than 5 years. Plasma cell leukemia is also a rare form of plasma cell dyscrasia (2% to 4% of all myelomas). The primary form accounts for 60% of the cases. In primary PCL, the constellation of adverse biologic prognostic factors in patients with advanced aggressive myeloma is already present at diagnosis. In fact, primary PCL has a more aggressive clinical presentation than MM, with a higher frequency of extramedullary involvement, anemia, thrombocytopenia, hypercalcemia, and renal failure. Treatment with a single alkylating agent plus prednisone is not appropriate. Combination chemotherapy with VAD, cyclophosphamide and etoposide, or VCMP/VBAP is a better initial option. Given the poor prognosis of primary PCL, intensification with high-dose therapy followed by stem cell rescue should be offered to affected patients.