It is a translational research study with mechanistical objectives and including biological samples of patients with thrombocytopenia

This study is a prospective study to collect blood, bone marrow and hair bulb from patients with thrombocytopenia, to better understand the mechanism of idiopathic chronic thrombocytopenia of undetermined significance (ICTUS)

Inclusion Criteria:

• Age: 18-80
• Nosological criteria for thrombocytopenic patients:
• ICTUS: acquired thrombocytopenia lasting>6 months, without feature of dysimmunity (antiplatelet Ab, or anti nuclear Ab, anti ENA Ab, ANCA, anti-CCP Ab, cryoglobulinemia), normal bone marrow examination, absence of other thrombocytopenia in the family. All ICTUS patients included in the study will thus have a bone marrow aspiration.
• ITP: Diagnosis of ITP is made according to the international ITP consensus (diagnostic criteria of Rodeghiero){Provan, 2010 #18}, knowing that a presumptive diagnosis of ITP is made when the history, physical examination, complete blood count, and examination of the peripheral blood smears do not suggest other etiologies for the thrombocytopenia. There is no "gold standard" test that can reliably establish the diagnosis. We are concerned that this group of patients may include ICTUS patients.
• ITP with immunological features: ITP with detectable anti-platelet antibodies (Ab) and/or autoimmunity (anti nuclear Ab, anti ENA Ab, ANCA, anti-CCP Ab, cryoglobulinemia), and/or previously responsive to immunomodulatory ITP-directed therapies (steroids, intravenous Immunoglobulin, rituximab, splenectomy). We will use these patients as non-ICTUS, ITP positive controls.
• Thrombocytopenic myelodysplasia: platelets <150 G/l and diagnosis of myelodysplasia according to the WHO classification (abnormal bone marrow features).
• Healthy controls: patients with normal blood counts undergoing cardiovascular surgery for valve replacement, or healthy bone-marrow donors.
• Affiliated person or beneficiary of a social security scheme. Free, informed and written consent signed by the participant and the investigator (at the latest on the day of inclusion and before any examination required by the research).

Exclusion Criteria:

• Age under 18 or over 80
• Persons placed under judicial protection,
• Persons participating in another research including a period of exclusion still in course
• Persons in emergency situation,
• Pregnant or nursing women,
• Women of childbearing age who do not benefit from effective contraception (HAS criteria),
• Brain death or deceased persons,
• Person who doesn't speak French, doesn't read it, doesn't write it, and doesn't have a schooling in France.

In this project we will study 30 patients with ICTUS, 20 ITP with immunological features, 20 MDS patients and 10 Healthy volunteers (normal bone marrow donors, obtained during a sternotomy performed in the cardiac surgery unit).