TTP as a function of age of onset and mechanism for ADAMTS13 deficiency. The proportions of adulthood-/childhood-onset TTP and acquired/inherited TTP, respectively, presented in this figure were calculated from the data of the French Registry for TTP (840 patients).^10,13  These data are in agreement with miscellaneous demographic data reported in the literature by other teams.^3,5-9  The diagram shows 100 patients with TTP, each patient being represented by a symbol, either a square for patients with adulthood-onset TTP (91%) or a circle for patients with childhood-onset TTP (9%). Acquired TTP is presented in blue (94.5%), and inherited TTP (USS) in red (5.5%). Interestingly, the proportion of USS is very low (2.5%) in adulthood-onset TTP, whereas it is as high as 33% in childhood-onset USS.