Fatal congenital thrombotic thrombocytopenic purpura with apparent ADAMTS13 inhibitor: in vitro inhibition of ADAMTS13 activity by hemoglobin

Severe ADAMTS13 deficiency in thrombotic thrombocytopenic purpura (TTP) is either constitutional and caused by ADAMTS13 mutations, or acquired and most often due to ADAMTS13 inhibitory autoantibodies. In strongly hemolytic serum of a pediatric patient, diagnosed with TTP postmortem, ADAMTS13 activity was less than 3%. Both parents had an ADAMTS13 activity of approximately 50%. Sequencing of the ADAMTS13 gene revealed an intronic 687-2A>G...