Association among genotype severity score, plasmatic activity of ADAMTS13, age at first TTP episode requiring FFP, and annual rate of TTP episodes. Increasing severity in the genotype score (ie, an increasing number of N-terminal mutations; mild genotype indicates 2 C-terminal mutations; moderate genotype, 1 C- and 1 N-terminal mutations; and severe genotype, 2 N-terminal mutations) was associated with lower plasmatic activity of ADAMTS13 (A), earlier age at first TTP episode requiring FFP (B), and a higher annual rate of TTP episodes (C).