Inclusion Criteria:  Confirmed diagnosis of an acute episode of acquired thrombotic thrombocytopenic purpura Treatment with at least one single dose of caplacizumab (10 mg i.v. or s.c.) Male or female patients ≥ 18 years of age signed written informed consent  Exclusion Criteria:  Hereditary thrombotic thrombocytopenic purpura disability to give informed consent