Relationship among ADAMTS13 genotype, residual activity, and age at first episode requiring FFP. Shown is the age at first TTP episode requiring FFP and residual ADAMTS13 activity in multiple patients carrying the same mutations of ADAMTS13. A clustering of both the age at first TTP episode requiring FFP and the plasmatic activity of ADAMTS13 can be observed for patients with a given ADAMTS13 genotype. The clustering was observed both for related patients (the first 3 genotypes) and for unrelated individuals (the homozygous p.R1060W genotype). For each patient, ADAMTS13 activity (▵) and age of the first TTP episode requiring FFP (●) are aligned.