Inclusion Criteria:  Age ≥ 18 years ≤ 80years Diagnosis of ITP whatever the duration, according to the standard definition Platelet count ≤ 20 x 109/L Any cutaneous and/or any mucosal bleeding manifestations Affiliated to a social security regime Written consent from patient  Exclusion Criteria:  PCR SARS-CoV2 positive Life-threatening bleeding defined as Intracranial hemorrhage and/or active organ bleeding (GI tract, urinary tract or menorrhagia with at least a 2 g/dl decrease of hemoglobin value from baseline). Ongoing anticoagulation treatment (Therapeutic Low molecular weight heparins (LMWHs), direct oral anticoagulants (DOACs) and vitamin K antagonists (VKAs)) Previous non-response to IVIg or DEX Treatment with prednisone (1 mg/kg per day) for more than 3 days Any, contraindications to the prescribed Ig IV or prednisone patent medicine and to Neofordex® Ongoing severe infection Severe Renal insufficiency (DFG < 45 ml.min.1.73m2) Severe Cardiac insufficiency (FEVG < 30 %) Ongoing viral infection (HIV, Viral hepatitis, herpes, varicella, zona). Uncontrolled diabetes Psychotic state not yet controlled by treatment Inability or refusal to understand or refusal to sign the informed consent from study participation Persons deprived of their liberty by judicial or administrative decision, Persons under legal protection (guardianship, curatorship) Pregnant or breastfeeding woman or ineffective contraception Participation in another interventional study involving human participants or being in the exclusion period at the end of a previous study involving human participants.