Distinct clinical and genetic characteristics of myelodysplastic syndrome in younger patients.

Myelodysplastic neoplasms (formerly myelodysplastic syndromes, MDS) are heterogeneous clonal haematological malignancies that primarily affect the elderly, though a notable proportion of patients are diagnosed at younger ages. We retrospectively analysed 1437 patients diagnosed or treated at Asan Medical Center between 1989 and 2022, comparing clinical and genetic characteristics by age group. Younger patients (≤50 years) demonstrated improved overall survival (OS) and leukaemia-free survival (all p < 0.001), a higher proportion of females, lower platelet levels, reduced bone marrow blasts, decreased mutation burden and lower scores on the International Prognostic Scoring System. In contrast, the response rates to hypomethylating agents did not significantly differ between age groups (p = 0.543); however, SF3B1 mutation predicted favourable therapeutic response. Mutations in ASXL1, DDX41, DNMT3A, RUNX1, SF3B1, SRSF2, TET2, TP53 and ZRSR2 occurred more frequently in older MDS patients, whereas SAMD9 mutations predominated in younger cohort. In patients undergoing allogeneic haematopoietic stem cell transplantation (HSCT), OS did not differ significantly between younger and older patients; only TP53 mutation reliably predicted inferior post-HSCT OS (hazard ratio 3.099, p = 0.003). In analyses limited to younger patients, the presence of DNMT3A, TP53 and U2AF1 mutations was associated with worse OS. These findings suggest that younger patients represent a biologically distinct subset of MDS.