Pediatric Myelodysplastic Syndrome (p-MDS) comprises a heterogeneous group of clonal hematopoietic stem cell diseases with an increased risk of evolution to Acute Myeloid Leukemia (AML). Cytogenetic is one of the most important prognostic factors for MDS and it is present into score prognostic systems as the Revised International Prognostic Scoring System (IPSS-R). Chromosomal translocations are rare cytogenetic abnormalities in de novo MDS. Therefore, their reporting is essential for the identification of new cytogenetic prognostic risk groups and possible alterations associated with the MDS pathogenesis.The aim of this study was describe a yet unreported der(2)t(2;15)(q37;q21) in a de novo p-MDS associated with evolution to AML.

Cytogenetic analysis was performed in Bone Marrow (BM) cells by G-banding. Fluorescence In Situ Hybridization (FISH) was performed to investigate the possible rearrangement involving chromosomes 2 and 15, using a Whole Chromosome Painting (WCP) probe for chromosome 2 and LSI PML/RARA for chromosome 15 (PML gene).

A 12-year-old girl was admitted to the Pediatrics Institute of Federal University of Rio de Janeiro in January 2022. Peripheral blood count showed Hemoglobin (Hb) level of 6.5 g/dL, 794.000 platelets/mm3, and 2.600 white blood cell (WBC)/mm3. The myelogram showed dysplasias and 16% of myeloid blasts being classified with MDS-EB-t. The conventional cytogenetic analysis showed the karyotype: 46,XX,add(2)(q37?)[25]. Using molecular cytogenetic methods, we characterized the chromosomal alteration as an unbalanced translocation involving chromosomes 2 and 15. This translocation was observed in 71.6% (190/265) of the interphase nuclei and metaphases. The final karyotype was: 46,XX,der(2)t(2;15)(q37;q21)[25]. Five months later, the patient showed in the myelogram 50.7% of blast cells compatible with AML. The patient was indicated for allogeneic Hematopoietic Stem Cell Transplantation (HSCT) and initiated chemotherapy.

In p-MDS, chromosomal translocations as sole chromosomal abnormality are rare and their real prognostic impact is unknown. The patients with this type of cytogenetic alteration are classified as intermediate-risk group according to the IPSS-R. Our report describes the clinical outcome in a novo p-MDS showing a der(2)t(2;15)(q37;q21). A broad scientific review showed that the der(2)t(2;15)(q37;q21) was not yet reported in p-MDS. It is interesting to note that this chromosomal translocation was associated with a poor clinical outcome, with progression from MDS to AML. The cytogenetic and clinical features were important tools for the indication to allogeneic HSCT.

This study and literature review highlight the importance of cytogenetics and clinical follow-up of de novo p-MDS patients for the identification for HSCT. This is the first study that describe the der(2)t(2;15)(q37;q21) in a p-MDS associated with AML evolution.