Germline and somatic genetic landscape of pediatric myelodysplastic syndromes.

Pediatric myelodysplastic syndromes (MDS) represent a rare group of clonal hematopoietic stem cell disorders accounting for approximately 5% of pediatric hematologic malignancies. They are characterized by ineffective hematopoiesis, cytopenia, and dysplastic changes in the bone marrow with variable risk of progression to acute myeloid leukemia. Unlike adult MDS, pediatric cases predominantly present with hypocellular bone marrow, with monosomy 7 and trisomy 8 as the most common cytogenetic aberrations. Pediatric MDS can manifest as primary disease or arise secondary to classical inherited bone marrow failure syndromes, prior cytotoxic therapy, or acquired aplastic anemia. In recent years, new germline syndromes have been identified in a substantial proportion of patients with "primary" MDS. The most common are GATA2 deficiency and SAMD9/SAMD9L syndromes, accounting for at least 7% and 8% of cases, respectively. The somatic mutational landscape is different from adult MDS, with recurrent mutations affecting SETBP1, ASXL1, RUNX1, and RAS pathway genes (PTPN11, NRAS, KRAS, CBL), while mutations in spliceosome components and epigenetic regulators, which are common in adults, are virtually absent in children. Monosomy 7 serves as a "central hub" in disease evolution, associating with somatic leukemia driver mutations. On the other hand, somatic UBTF-TD and NPM1 mutations define a subtype of MDS with excess blasts with predominantly normal karyotype without known germline predisposition. Hematopoietic stem cell transplantation is the only curative option for pediatric MDS. Understanding the unique genetic profile of pediatric MDS has implications for diagnosis, therapy, donor selection and long-term surveillance, particularly for patients with germline predisposition syndromes. This review discusses current classification systems (WHO and ICC), provides a detailed overview of the germline and somatic genetic landscape of pediatric MDS, and highlights clinical implications of these genetic alterations.