1. Challenges in recognizing and diagnosing TA-TMA
TA-TMA is difficult to recognize as complex clinical picture post-HSCT can mask or mimic TA-TMA, such as cytopenia due to marrow aplasia before engraftment, drug-induced hypertension and immune-mediated hemolysis. Besides, as not all features appear simultaneously and may evolve over days to weeks, high index of suspicion is crucial to pick up subtle cues of evolving TA-TMA such as persistent hypertension requiring multiple anti-hypertensives, elevated LDH, or increased transfusion requirement and platelet refractoriness. There has yet been a universally accepted diagnostic criteria for TA-TMA. Histology is the most reliable modality yet invasive and risky. Diagnostic triad of hypertension, thrombocytopenia and elevated LDH proposed by Dvorak (2) provides useful guidance in recognizing TA-TMA, though proteinuria instead of thrombocytopenia is the third universal feature in local cohort (Table 1b) .