Microangiopathic

Microangiopathic describes diseases that affect the microvasculature—the smallest vessels, including capillaries, arterioles, and venules. These disorders are often marked by endothelial injury and formation of microthrombi within small vessels. A hallmark is microangiopathic hemolytic anemia, where circulating red blood cells are damaged as they traverse obstructed or stiffened microvessels.

Pathophysiology involves endothelial injury with platelet activation and thrombus formation in the microcirculation. Mechanical destruction of red blood cells yields schistocytes and nonimmune hemolysis. Lab findings include anemia with reticulocytosis, elevated LDH, indirect bilirubin, decreased haptoglobin, and often thrombocytopenia. Renal and neurologic symptoms may accompany the process.

Major contexts include thrombotic microangiopathy (TMA) such as thrombotic thrombocytopenic purpura (TTP) and atypical HUS; disseminated intravascular coagulation; and drug- or infection-associated microangiopathies. Triggers include Shiga toxin, complement dysregulation, autoimmune disease, pregnancy-related disorders (e.g., HELLP), malignancy, and certain medications (chemotherapy, calcineurin inhibitors).

Diagnosis relies on a blood smear showing schistocytes alongside hemolysis, thrombocytopenia, and organ involvement. Etiologies are distinguished by ADAMTS13 activity for TTP, complement studies for atypical HUS, and coagulation testing for DIC.

Management targets the underlying cause with supportive care. Plasma exchange is standard for TTP; complement inhibitors may treat atypical HUS; treat infections and remove offending drugs; renal replacement therapy may be needed for kidney failure. Prognosis varies by condition, and prompt treatment improves outcomes.