3]. TTP can be congenital, due to homozygous or compound heterozygous mutations of ADAMTS13 (Upshaw-Schulman syndrome) or acquired (aTTP) [4]. The latter is caused by inhibitory ADAMTS13 antibodies [2,4]. Diminished metalloprotease activity below 10% of normal differentiates TTP from other forms of TMA [1,4]. Intensive plasma exchange (PLEX) therapy combined with immunosuppression has improved the previously dismal outcome of aTTP [2,4]. This evidence concerns the gene ADAMTS13 and congenital thrombotic thrombocytopenic purpura.