IN VITRO ANALYSIS OF HEMATOPOIETIC PROGENITORS IN THE SYNDROME OF THROMBOCYTOPENIA WITH ABSENT RADIUS

Abstract

The syndrome of thrombocytopenia with absent radius (TAR) is an autosomal recessive condition with poorly-understood hematologic abnormalities including a leukemoid reaction and hypomegakaryocytic thrombocytopenia. We studied bone marrow and serum from an infant with TAR using soft agar and plasma clot cultures of hematopoietic progenitor cells.Consistent with the near absence of CFU-Meg in this patient was the observation that the serum level of megakaryocyte colony stimulating activity (Meg-CSA) was markedly increased. TAR serum stimulated the growth of normal CFU-Meg from adult peripheral blood (82 colonies with TAR serum v. 0 colonies with normal AB serum). These in vitro data suggest that the hematologic defect in TAR is at the level of the megakaryocyte stem cell, and that normal humoral regulation of megakaryopoiesis is retained. Study of the patient's parents is in progress.