Shortened platelet half-life in multiple myeloma.

Various defects in platelet function have been reported as being associated with multiple myeloma. In 30 myeloma patients and 15 healthy controls, we investigated platelet survival using in vitro labeling of autologous platelets with 111indium-oxine and measuring the in vivo kinetics of the radioisotope. Significantly shortened platelet half-life in patients averaged 73 hours, while platelet half-life in the healthy controls averaged 107 hours. In myeloma patients, serum levels of thromboxane B2, beta-thromboglobulin, and platelet factor 4 were significantly elevated; aggregation indices were within the pathological range; platelet counts and spleen-liver indices, however, were comparable to those of the healthy control group. No statistical correlation was found between platelet half-life and paraprotein concentrations. Our findings suggest an initial--so far unexplained--intravascular process of platelet activation and consumption that finally manifests in shortened platelet half-life. It seems that overt thrombocytopenia develops only when the compensatory capacity of the bone marrow finally becomes exhausted. Further studies should be able to elucidate the pathophysiologic processes involved.