Is IgD Myeloma a Separate Clinical Entity? Report of Six Cases Investigated by Isoelectric Focusing

Six IgD myeloma patients whose monoclonal components were identified by isoelectric focusing are presented. They represented 4% of all patients with myeloma seen at our institute between 1982 and 1986. The patients did not display many of the features described as typical for IgD myeloma: in particular younger age group, decreased survival and increased incidence of lymphadenopathy, hepatosplenomegaly, extraosseous disease, anemia, renal failure and hypercalcemia. However males predominated, the concentrations of circulating monoclonal IgD were low and concentrations of serum and urinary monoclonal free light chains were high, findings previously reported in IgD myeloma. The concentrations of circulating IgD were at the lower end of ranges reported previously. The hypothesis that our patients represent the malignant equivalent of the normal "low secretory phenotype", possibly associated with improved survival, is discussed. The belief that IgD myeloma is a separate clinical entity is questioned. The sensitive, high-resolution technique of isoelectric focusing is recommended as the investigation of choice for the detection of monoclonal gammopathies in body fluids.