Thrombotic microangiopathy overlap syndrome in pregnancy

In these two cases, we highlight the concept of pregnancy-associated thrombotic microangiopathy (TMA) overlap syndrome, where two different TMAs occur together, likely one driving another. Thrombotic microangiopathies occurring in pregnancy threaten the lives of both mother and fetus, and yet precise diagnosis may be difficult because of overlapping clinical and laboratory features. The three main syndromes to be considered are thrombotic thrombocytopenic purpura (TTP) - an acute disorder caused by severe ADAMTS13 deficiency; preeclampsia/HELLP syndrome - characterised by haemolysis, elevated liver enzymes, and low platelets; and atypical haemolytic uremic syndrome (aHUS)- most commonly caused by mutations in the complement regulatory genes. We present two cases where the combination of two TMAs (one most likely driving the other) led to difficult management dilemmas.