Measurements of ADAMTS13 activity, ADAMTS13 inhibitor, and ADAMTS13 autoantibodies are useful in diagnosing TTP, guiding its therapy, and predicting possible relapse.[8,9] ADAMTS13 is an essential component in the pathophysiology of TTP.[10] ADAMTS13 can stimulate complement pathways and inflammatory cytokines, such as IL-6 and IL-10, and autoreactive B and T cells.[11] Regarding the immune abnormalities in TTP and HLH, overlapping immune dysregulation is the principal association between these 2 diseases. The gene discussed is ADAMTS13; the disease is thrombotic thrombocytopenic purpura.