Thrombotic Thrombocytopenic Purpura: Report of a Case With Disseminated Intravascular Platelet Aggregation

The nature and etiology of the vascular occlusions encountered in thrombotic thrombocytopenic purpura (TTP) have been subject to controversy for a number of years. Disseminated platelet thrombosis has been suggested in the earlier literature, although later views have favored fibrin thrombi resulting from vascular damage or disseminated intravascular coagulation (DIC). The serial coagulation study and the lightand electron-microscopic findings in a case of TTP are described here. The multiple vascular occlusions were due to the presence of densely packed platelet aggregates in which a variable quantity of fibrin was present. Less commonly, loose platelet aggregates were noted. Fibrin under the endothelial lining was occasionally observed in relationship to the vascular occlusion and was thought to be secondary to the release of various substances from aggregating platelets. The serial coagulation study and the histologic examination of tissues showed no evidence of disseminated intravascular coagulation. This case shows that the occlusions observed in TTP can be due to disseminated intravascular platelet aggregation in the absence of DIC. Although TIP might be of variable etiology, it is felt that cases showing disseminated intravascular platelet aggregation should be distinguished from DIC in order to plan therapy on a rational basis.