Rare presentation of serous effusions in pediatric acute myeloid leukemia: insights from a retrospective case series

Serous effusions are rare extramedullary manifestations of pediatric acute myeloid leukemia (AML), for which limited data are available. This study aimed to systematically characterize the clinical features, biological profiles, and outcomes of pediatric AML patients who presented with serous effusions. A retrospective case series was conducted at Beijing Children’s Hospital and Beijing Children’s Hospital Baoding Hospital from January 2015 to December 2024. Pediatric patients newly diagnosed with AML or isolated myeloid sarcoma presenting with serous effusion were included. Seven children (six males and one female) were included. The median time from symptom onset to diagnosis was 30 days (range: 10–150 days). Initial white blood cell counts ranged from 3.39 × 10⁹/L to 212.13 × 10⁹/L, with two patients exhibiting hyperleukocytosis. Genetic alterations included KMT2A rearrangements (4/7), RUNX1::RUNX1T1 fusions (2/7), and SFPQ::ZFP36L2 fusion (1/7). All patients had pleural effusions, and six had pericardial effusion. Four patients had additional extramedullary involvement. The median follow-up was 12.0 months (range: 1.0–68.0 months). Owing to critical illness, six of the seven patients received induction therapy in the intensive care unit. One patient died after induction therapy because of severe acute suppurative appendicitis and sepsis; the remaining six patients underwent hematopoietic stem cell transplantation. At the last follow-up, four patients were alive, while two died of early relapse following stem cell transplantation. Serous effusion is a rare manifestation of pediatric AML, which is observed in patients with high-risk genetics and is often accompanied by a critical clinical course necessitating intensive care. Further studies are needed in this subgroup.