REFRACTORY THROMBOCYTOPENIA WITH CHROMOSOME 11Q23 ABNORMALITY

Although cytopenia is a common manifestation of myelodysplastic syndro me (MDS), isolated thrombocytopenia is rare. The term ''refractory thr ombocytopenia'' (RTC) has been proposed as a counterpart of refractory anemia. We describe here a case of RTC associated with chromosome abn ormality on 11q23, A 59-year-old man was admitted because of severe th rombocytopenia. A bone marrow examination revealed an increased number of micromegakaryocytes and the absence of normal-sized megakaryocytes without obvious dysplasia in either the myeloid or the erythroid line age. A remarkable increase of GPIIb/IIIa (CD41a)-positive precursor ce lls in the bone marrow was observed. Cytogenetic examination detected the chromosome abnormality, an addition on chromosome 11q23. Transloca tion of the HRX gene was not detectable by Southern blot analysis. The diagnostic problems of isolated thrombocytopenia and possible partici pation of gene(s) on chromosome 11q23 in megakaryocytopoiesis as well as early hematopoiesis are discussed.