Efficacy and Safety of Immunosuppression, Caplacizumab and Plasma Infusion Without Therapeutic Plasma Exchange in Immune-mediated Thrombotic Thrombocytopenic Purpura

Inclusion Criteria: * Adult patient ≥ 18 years; * Clinical diagnosis of iTTP based on standard clinical and laboratory criteria (French Score ≥ 2): i.e., thrombotic microangiopathy syndrome with platelet count ≤ 30 G/L and serum creatinine ≤ 200 μmol/L; it is not necessary to have the laboratory result confirming the severe ADAMTS13 deficiency for inclusion of patient \[32\] (For patient with previous TTPflare, French score can be \< 2); * Patient having read and understood the information letter and signed the Informed Consent Form. If the patient is unable to express his consent, the consent will be signed by his representative ((1) the trusted person, or failing that, (2) a family member, or (3) a close relative of the person concerned). In this case, consent to continue the study will subsequently be requested from the patient (article L1122-1-1 of the CSP); * Patient affiliated with, or beneficiary of a social security (national health insurance) plan; * For women: * Women of childbearing potential : * Effective contraception according to WHO definition (estrogen-progestin or intrauterine device or tubal ligation) since at least 1 month and; * Negative blood pregnancy test; * Women surgically sterile (absence of ovaries and/or uterus); * Postmenopausal women (non-medically induced amenorrhea for at least 12 months prior to the inclusion visit). Exclusion Criteria: * Platelet count \> 100 G/L before plasma treatment; * Patients with a French score \< 2 (a serum creatinine level \> 200 μmol/L and/or with a platelet count \> 30 G/L), in order to exclude possible cases of hemolytic uremic syndrome (except for patient with previous TTPflare, French score can be \< 2); * Other known causes of cytopenias and/or organ failure including but not limited to: uncontrolled cancer, chemotherapy, transplant, drugs, HIV at AIDS stage; * Patients with a severe neurological disorder i.e. seizure, coma, focal deficiency, trouble of consciousness; * Pregnant women (positive result from a blood pregnancy test) or patients with an imminent project of pregnancy; breastfeeding women (due to lack of pharmacological data for caplacizumab during pregnancy and breastfeeding); * Weight \> 100KG; * Congenital TTP; * Clinically significant active bleeding or high risk of bleeding (excluding thrombocytopenia); * Chronic treatment with anticoagulant that cannot be interrupted safely, including but not limited to: vitamin K antagonists, direct oral anticoagulant, low molecular weight heparin or heparin; * Malignant hypertension; * Contra-indication to CABLIVI 10 mg powder and solvent for solution for injection: hypersensitivity to caplacizumab or to any of the excipients; * Contra-indication to Plasma treatment; * Contra-indication to corticosteroid (= ((methyl)prednisone or (methyl)prednisolone)) or excipients; * Contra-indication to rituximab or excipients and to its premedication; * Person deprived of liberty by administrative or judicial decision or placed under judicial protection (guardianship or supervision); * Participation in another drug interventional clinical trial within 30 days prior to inclusion and during the study.