Idiopathic thrombocytopenic purpura (ITP) is the most frequent auto-immune cytopenia. There is no specific biological marker and the diagnosis often results from the exclusion of other differential diagnoses, notably inherited thrombocytopenia.

Recent studies have reported an original platelet destruction mechanism in ITP, by antibody-mediated desialylation of membrane proteins. The detection of platelet sialylation can be readily achieved using flow cytometry. This could provide a new biomarker of ITP, useful to ascertain a diagnosis of ITP and guide towards proper patient management.

Inclusion Criteria:

• Adult patients (>18yo) with a diagnosis of ITP (primary acute, persisting or chronical)
• Adult patients (>18yo) with a diagnosis of non immunological thrombocytopenia (constitutive thrombocytopenia, myelodysplastic syndrome, chemotherapy-induced thrombocytopenia)
• Adult patients (>18 yo) without thrombocytopenia
• Enrolled in a Social Security system
• Having provided informed consent

Exclusion Criteria:

• Minor patients (<18 yo)
• Enrolled in another clinical study
• Having received corticosteroids or polyvalent immunoglobulins in the past 4
• weeks or anti-platelet therapy or NSAID during the past 7 days
• Having received platelet transfusion in the past fortnight
• With proven iron deficiency
• With drug-induced immune-allergic thrombocytopenia.
• Pregnant and breastfeeding women,
• guardian patients, will be excluded from this population.

3 Populations will be recruited in the study:

Number of topics planned:

50 Patients in the PTI group 50 patients in the non-immunological thrombocytopenia group 50 patients in the control group