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Clinical features, prognosis and factors influencing survival, as well as long-term evolution of the disease were analyzed in 130 patients with myelodysplastic syndromes (MDS) with particular reference to the refractory anemia with excess of blasts (RAEB). Survival of patients with 3 FAB subtypes, RAEB, RAEB in transformation (RAEB-T) and chronic myelomonocytic leukemia (CMMoL) showing excess blasts was uniformly poor relative to primary acquired refractory anemia (PARA) and primary acquired sideroblastic anemia (PASA). The degree of cytopenias, karyotypic abnormalities, bone marrow cellularity, transition to acute leukemia were not reliable prognostic parameters for discrimination of RAEB with poor or good prognosis. Disease transition was frequently observed in our MDS patient population, at an overall incidence of 37.7%. Transition of PARA to RAEB occurred after a prolonged course in some patients.

The clonal composition of each cell population was determined from the characteristic methylation pattern of DNA and the restriction fragment length polymorphism (RFLP) of the hypoxanthine phosphoribosyltransferase (HPRT) and phosphoglycerate kinase (PGK) genes, both located on the X chromosome. About 71% of Japanese females are heterozygous in terms of the RFLP of either HPRT or PGK genes, which was demonstrated by using 5' genomic DNA or cDNA probes for these genes. All 3 cases of chronic myeloproliferative disorders showed monoclonal patterns. AML or ALL cases demonstrated either monoclonal or polyclonal patterns depending upon the percentage of blastic cells. Monoclonal patterns were seen in 3 of 4 cases of myelodysplastic syndromes and both PNH cases.