Elevated platelet count and megathrombocyte number in sickle cell anemia.

Eight adult patients with sickle cell anemia were followed over a 6-mo period. During this time all patients had elevated plateletcounts, 1.7-fold (mean, 438,398 +/- 86,223), and megathrombocyte numbers, 2.3-fold (mean, 79,535 +/- 38,907), during asymptomatic periods. These data are interpreted as suggesting that the elevated platelets and megathrombocytes in asymptomatic sickle cell patients result from lack of splenic sequestration. During three crises in two patients, both megathrombocyte number and platelet count fell significantly. It is speculated that platelets may be associated with the pathology in this disease. Platelet function studies performed during crises, therefore, must take into account the number of megathrombocytes.