Transient abnormal myelopoiesis in down syndrome: Turkish society of pediatric hematology data

Transient abnormal myelopoiesis (TAM) is a self-limiting clonal myeloproliferative disorder occurring in approximately 5–30% of neonates with Down syndrome (DS). Although TAM resolves without requiring any treatment in most patients, 10–23% experience early death due to TAM-related complications, and 19–30% subsequently develop Down syndrome-related myeloid leukemia (DS-ML) within the first few years of life. This retrospective multicenter study included 51 patients with DS and TAM from 17 centers in Türkiye. Within 6 months after TAM diagnosis, early mortality attributable to TAM-related complications occurred in 10% of patients (n = 5), while an additional 10% (n = 5) died from causes unrelated to TAM. Exploratory unadjusted competing-risk analyses suggested differences in the 6-month cumulative incidence of TAM-related death across several severe clinical and laboratory subgroups; these findings were based on only five TAM-related deaths and were not adjusted for multiple comparisons. The complete clinical and hematological resolution of TAM was observed in 38 patients (75%). Among the 41 patients who survived the early period, 13 developed DS-ML (32%, 13/41), corresponding to 26% (13/51) of the entire cohort. Among these 13 patients, one died due to progressive disease, and two died due to infections, while the estimated 2-year overall survival (OS) after DS-ML diagnosis was 84.6% (95% CI, 51.2–95.9%). In the entire TAM cohort, the estimated 3-year OS and event-free survival (EFS) rates were 71.5% (95% CI, 55.4–82.6%) and 47.4% (95% CI, 31.2–61.9%), respectively, and remained unchanged at 5 years. In addition, a substantial proportion of patients subsequently developed DS-ML, supporting the need for careful long-term follow-up even after complete resolution of TAM. Clinical trial number: Not applicable.