Familial bleeding tendency associated with microcytic platelets and impaired release of platelet adenosine diphosphate

This report describes a familial bleeding tendency associated with abnormal platelet responses to adenosine diphosphate (ADP), connective tissue suspension, thrombin, and kaolin, which were attributed to impaired platelet ADP release. All but one of the patients also had microcytic platelets. The association of microcytic platelets with impaired platelet ADP release may be due to a population of predominantly old platelets in these patients.