Based on the scope of the scientific literature and the national registries for TTP since 2001, ~150 different cases of child-onset iTTP with a documented severe functional deficiency of ADAMTS13 (activity < 10 IU/dL per definition) and the presence of anti-ADAMTS13 autoantibodies have been reported [13,14,15,16,17,18,19,20,21,22,23,24,25]. This evidence concerns the gene ADAMTS13 and thrombotic thrombocytopenic purpura.