Thrombotic microangiopathies

Thrombotic microangiopathy
Micrograph of thrombotic microangiopathy with the characteristic onion-skin layering seen in older lesions. PAS stain.
Classification and external resources
Specialty	rheumatology
ICD-10	M31.1
ICD-9-CM	446.6
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Thrombotic microangiopathy (TMA) is a pathology that results in thrombosis in capillaries and arterioles, due to an endothelial injury. It may be seen in association with thrombocytopenia, anemia, purpura and renal failure.

The classic TMAs are hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. Other conditions with TMA include atypical hemolytic uremic syndrome, disseminated intravascular coagulation, scleroderma renal crisis, malignant hypertension, antiphospholipid antibody syndrome, and drug toxicities, e.g. calcineurin inhibitor toxicity.

The clinical presentation of TMA, although dependent on the type, typically includes: fever, microangiopathic hemolytic anemia (see in a blood smear), renal failure, thrombocytopenia, neurological manifestations. Generally, renal complications are particularly predominant with Shiga-toxin-associated hemolytic uremic syndrome (STx-HUS) and atypical HUS, whereas neurologic complications are more likely with TTP. Individuals with milder forms of TTP may have recurrent symptomatic episodes, including seizures and vision loss. With more threatening cases of TMA, and also as the condition progresses without treatment, multi-organ failure or injury is also possible, as the hyaline thrombi can spread to and affect the brain, kidneys, heart, liver, and other major organs.

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