THROMBOCYTOPENIA WITH ABSENT RADII SYNDROME - STUDIES ON SERUM THROMBOPOIETIN LEVELS AND MEGAKARYOPOIESIS IN-VITRO

Purpose: The pathogenesis of thrombocytopenia in patients with thrombo cytopenia with absent radii (TAR) syndrome has not been clarified yet. Patients and Methods: This is the first report of a Japanese patient with TAR syndrome. We studied his megakaryopoiesis in vitro and serum levels of thrombopoietin (TPO). Results: Serum levels of TPO in the pa tient with TAR syndrome were comparable with those of an age-matched c ontrol. The bone marrow cells from the patient with TAR syndrome actua lly generated megakaryocyte colonies in the presence of TPO and the nu mbers were significantly greater than those from the age-matched contr ol marrow. However, megakaryocyte colonies from the marrow cells with TAR syndrome contained a much lower number of cells per colony and the size of the individual megakaryocytes appeared to be smaller. Conclus ion: These data suggest that megakaryocyte progenitors from patients w ith TAR syndrome may have decreased proliferative and differentiative capacity to respond to TPO, leading to thrombocytopenia.