21 hematology centers in Turkey will participate in this noninterventional observational study. The recruitment target is 960 cases. Patients will be followed-up at least 1 year or to the end of the study according to the physicians' discretion, or withdrawal of consent. Recruitment period will be 36 months. Data will be collected via electronic case report form. Since the study cohort does not include only newly diagnosed patients, all aTTP patients will be included to the study, previous treatments and diagnosis information data could also be collected from hospital records. Patients recruitment duration: 3 years (36 months) Patients follow-up duration: 1 year (12 months)

Because of the non-interventional nature of the study, there is no predefined treatment protocol. The patients will be treated according to the routine practices of the centers. In observational drug studies, the drug to be administered in treatment should be prescribed and patient's treatment should be started prior to study inclusion decision is made as a principle. The participating physician will continue to treat the patients according to their routine practices. Not only newly diagnosed patients, all aTTP patients within participated centers will be recruited and 12 months follow-up data will be collected. 21 hematology centers in Turkey will participate in this noninterventional observational study. The recruitment target is 960 cases. Patients will be followed-up at least 1 year or to the end of the study according to the physicians' discretion, or withdrawal of consent. Recruitment period will be 36 months. Data will be collected via electronic case report form. Since the study cohort does not include only newly diagnosed patients, all aTTP patients will be included to the study, previous treatments and diagnosis information data could also be collected from hospital records. Patients recruitment duration: 3 years (36 months) Patients follow-up duration: 1 year (12 months)

Inclusion Criteria:

• Diagnosed as aTTP after 01.01.2015
• Patients with ADAMS13<10%
• Thrombocytopenia (<100.000)
• Coombs (-)
• Microangiopathic hemolytic amenia
• 18 years and older

Exclusion Criteria:

- Patient who does not sign informed consent form

Patients diagnosed with TTP and signed an informed written consent will be included into the study. Because of the non-interventional nature of the study, there is no predefined treatment protocol. The patients will be treated according to the routine practices of the centers. In observational drug studies, the drug to be administered in treatment should be prescribed and patient's treatment should be started prior to study inclusion decision is made as a principle. The participating physician will continue to treat the patients according to their routine practices. Not only newly diagnosed patients, all aTTP patients within participated centers will be recruited and 12 months follow-up data will be collected.