The differences in clinical features and prognosis between hypoplastic myelodysplastic syndrome (h-MDS) and normo-/ hypercellular MDS (NH-MDS) remain unsettled. In this study, the characteristics of 37 h-MDS patients and 152 NH-MDS patients were compared. Peripheral-blood white blood cell counts and bone marrow blast percentage were lower in h-MDS patients than in NH-MDS patients (P = 0.012 and 0.016, respectively). Refractory anemia (RA) was predominant (56.8% ) in h-MDS, whereas RA with excess of blast ( RAEB) was most common (44.7%) in NH-MDS. Chromosomal abnormalities -7/7q- occurred less frequently in h-MDS patients than in NH-MDS patients (0 vs 18.3%, P = 0.022). There was no significant difference in the prevalence of mutations of RAS, AML1, JAK2 , PTPN11, FLT3/ITD, and hypermethylation of SOCS1 and SHP1 between these two groups. International Prognostic Scoring System (IPSS) was ideal for predicting prognoses in h-MDS patients (P = 0.002). In low- or intermediate-1 (Int-1)-risk MDS patients, h-MDS patients had a superior survival than NH-MDS patients (P = 0.01). In conclusion, distinct from NH- MDS, h-MDS patients have different patterns of hemogram, distribution of French -American -British subtypes, cytogenetic changes and prognoses. IPSS is applicable in h- MDS as in NH- MDS. In patients with low- or Int-1-risk MDS, h -MDS patients have a better prognosis than NH-MDS patients. ; 附設醫院內科部 ; 醫學院附設醫院 ; 期刊論文