Epidemiology

TTP is a rare disorder with an average annual prevalence of around 10 cases per million people and an annual incidence of approximately one new case per million.[13][14][15] In one study, the age-gender standardised incidence of TTP and haemolytic uraemic syndrome was reported to be 6.5 cases per million per year in the US, 2.2 cases per million per year in the UK, and 3.2 cases per million per year in Saskatchewan, Canada.[16] Another study has estimated the incidence of TTP to be 4 to 11 cases per million per year in the US.[17] 

The incidence of TTP and haemolytic uraemic syndrome is higher in women and in black people.[17][16] In the US, between 65% and 75% of patients with TTP are women, and up to 44% are black.

Most patients with TTP subsequent to severe von Willebrand factor cleaving enzyme (ADAMTS-13) deficiency are between the ages of 20 and 59 years.[17] Another source reports an average age of 39 years (range, 19 to 71 years).[18]

TTP secondary to HIV infection has been reported in sub-Saharan Africa, most commonly in females (78%) and in those non-compliant with antiretroviral therapy (12.5%).[19]

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