Qualitative Platelet Abnormalities in Idiopathic Thrombocytopenic Purpura

Although idiopathic thrombocytopenic purpura (ITP) is generally believed to be a purely quantitative platelet disorder with normal platelet function, we observed impaired aggregation of platelets in nine of 11 patients with chronic ITP. The abnormalities were more severe in four patients with incomplete hematologic remission than in the seven patients in complete remissions. In three patients with intermittent ITP, platelet aggregation was normal. Globulin fractions from patients with both chronic and intermittent ITP inhibited aggregation of normal platelet-rich plasma with adenosine diphosphate and collagen. The globulin inhibitor of aggregation had characteristics of anti-platelet antibody. The functional platelet defects described may contribute to impaired hemostasis in ITP.