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thrombotic microangiopathy

Friday 15 April 2005

Definition: Thrombotic microangiopathy is a lesion seen in many conditions, including hemolytic uremic syndrome (HUS), radiation nephritis, toxicity related to various drugs, and hereditary forms.

Synopsis

fibrin thrombi within capillaries which may extend to arterioles

Pathogenesis

The term thrombotic microangiopathy (TMA) encompasses a spectrum of clinical syndromes that includes TTP and HUS. The common feature in both of these conditions is the widespread formation of hyaline thrombi, comprised primarily of platelet aggregates, in the microcirculation.

Consumption of platelets leads to thrombocytopenia, and the intravascular thrombi provide a likely mechanism for the microangiopathic hemolytic anemia and widespread organ dysfunction.

The varied clinical manifestations of TTP and HUS are related to differing proclivities for thrombus formation in specific microvascular beds.

Types

thrombotic thrombocytopenic purpura (TTP)
TTP is cmically associated with the pentad of fever, thrombocytopenia, microangiopathic hemolytic anemia, transient neurologic deficits, and renal failure.

hemolytic and uremic syndrome (HUS)

HUS is also associated with microangiopathic hemolytic anemia and thrombocytopenia but is clinically distinguished from TTP by the absence of neurologic symptoms, the prominence of acute renal failure, and frequent affliction of children.

Etiology (Exemples)

bone marrow allograft-associated thrombotic microangiopathy (15153944, 15077133, 10455370)