Essential athrombia: study of a new case.

A constitutional platelet function disorder in a twelve year-old girl characterized by a lifelong bleeding tendency, prolonged bleeding time, normal platelet count, normal clot retraction, normal platelet factor 3 activity and impaired platelet aggregation was reported. Platelet aggregation, studied turbidimetrically, was absent in the presence of usual doses of ADP (1-4 MUM) although a small wave of primary aggregation was obtained by very large ADP concentrations (25-50 muM). The platelets were also unresponsive to epinephrine, thrombin and diluted collagen suspensions. But an almost normal aggregation response occurred with strong collagen suspensions. The platelets responded to Ristocetin. Release of platelet ADP was found to be normal by collagen and thrombin, but impaired by kaolin. Platelet fibrinogen content was normal. The present case, investigated with recent methods, confirms the existence of a type of primary functional platelet disorder characterized solely by an aggregation defect, described in 1955 and 1962 under the name of "essential athrombia."