Syndromes of thrombotic microangiopathy associated with pregnancy

When a pregnant or postpartum woman presents with sudden and severe microangiopathic hemolytic anemia (MAHA) and thrombocytopenia, three syndromes that require urgent care must be considered: (1) preeclampsia with severe features/hemolysis, elevated liver function tests, low platelets (PE/HELLP) syndrome; (2) thrombotic thrombocytopenic purpura (TTP); and (3) complement-mediated thrombotic microangiopathy (C-TMA; also referred to as atypical hemolytic-uremic syndrome). The distinction among these three syndromes is often unclear because they share multiple clinical features. Overlap between PE/HELLP syndrome and the other two syndromes is also apparent from the fact that pregnancy can be a trigger for both TTP and C-TMA both before and after delivery and also the increased frequency of PE/HELLP syndrome in women who have recovered from TTP. When diagnostic criteria for PE/HELLP syndrome are present, management of hypertension and delivery is curative. Absence of improvement or actual progression of MAHA, thrombocytopenia, and kidney function abnormalities after delivery requires consideration of TTP and C-TMA. Minimal kidney involvement with severe thrombocytopenia suggests TTP and the need for treatment with plasma exchange; progressive kidney injury (in the absence of a cause for acute tubular necrosis) suggests C-TMA and the need for anti-complement treatment. We describe how we use these criteria to evaluate and manage pregnant/postpartum women with MAHA and thrombocytopenia.