Case Report: Central nervous system infiltration after allogeneic hematopoietic stem cell transplantation in high-risk myelodysplastic neoplasms.

BACKGROUND: Although central nervous system leukemia (CNSL) is a recognized complication of acute leukemia, myelodysplastic neoplasms (MDS) complicated by CNSL are exceedingly rare, particularly after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Previous studies have largely focused on chronic myelomonocytic leukemia with central nervous system (CNS) involvement. Here, we describe the first comprehensively documented case of isolated CNS infiltration after allo-HSCT in a patient with MDS. CASE PRESENTATION: A patient with high-risk MDS with increased blasts-2, harboring IDH1 and TP53 mutations, a complex karyotype, and a very high Molecular International Prognostic Scoring System score underwent unrelated allo-HSCT. On day +19 post-transplantation, the patient developed a severe, unexplained headache. Cerebrospinal fluid (CSF) analysis by flow cytometry revealed blasts largely immunophenotypically consistent with those in the bone marrow at initial diagnosis, while concurrent bone marrow assessment confirmed remission. CSF blasts were cleared following triple intrathecal therapy (IT). To date, the patient remains in remission on azacitidine maintenance therapy, with an overall survival of 14 months from diagnosis. CONCLUSION: Although CNSL is exceptionally rare in patients with MDS, this case demonstrates that isolated CNS infiltration may occur after allo-HSCT. Our findings emphasize that CNS involvement should be considered in the differential diagnosis of patients with MDS presenting with neurological manifestations, even without marrow relapse. Furthermore, this case highlights the critical role of CSF flow cytometry in establishing the diagnosis when conventional CSF studies are inconclusive.