Intrinsically impaired platelet production in some patients with persistent or chronic immune thrombocytopenia

Summary Persistent or chronic immune thrombocytopenias (P/C‐ ITP ) are acquired blood disorders lasting more than 3 months or 1 year, respectively. The pathogenesis of these disorders is thought to be immunological. We hypothesized that some patients with P/C‐ ITP might have an intrinsic megakaryopoiesis defect. We identified a group of P/C‐ ITP patients with acquired isolated mild thrombocytopenia (30–100 × 10 9 /l), undetectable anti‐platelet antibodies, negative autoimmune investigations and no need for treatment. We examined in vitro megakaryocyte differentiation and compared these patients' results with those of acute‐ ITP patients and healthy controls. No difference in proliferation, ploidy or expression of surface markers was found. In contrast, P/C‐ ITP patients had significantly fewer proplatelet‐forming megakaryocytes. This novel observation demonstrated that some patients diagnosed with P/C‐ ITP have an intrinsic megakaryopoiesis defect independent of the bone‐marrow environment. Further investigations are needed to dissect mechanisms underlying this impaired proplatelet formation in these patients.