The thrombotic microangiopathies.

The term thrombotic microangiopathy (TMA) encompasses a group of conditions that are defined by, or result from, a similar histopathological lesion. Hemolytic uremic syndrome (HUS), thrombotic thrombocytopenic purpura (TTP), and several other conditions are associated with TMA. Distinguishing HUS from TTP is not always possible unless there are specific causes, such as Shiga toxin, Streptococcus pneumoniae, or a specific molecular defect such as factor H or ADAMTS13 deficiency. This review describes the forms of HUS/TTP that are not related to Shiga toxin, pneumococcal infection, genetic causes, or ADAMTS13 deficiency. Conditions include HUS/TTP associated with autoimmune disorders, human immunodeficiency virus (HIV) infection, transplantation, malignancy, and medications.