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

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 9 109/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 thisimpaired proplatelet formation in these patients.

E. Riviere, J. F. Viallard, A. Guy, B. Kilani, J. Vieira-Dias, A. C. Pons, T. Couffinhal, J. L. Pellegrin and C. James.