Background: Pneumonia is a major cause of morbidity and mortality in children with acute lymphoblastic leukemia (ALL). However, detailed regional epidemiological data are scarce. This study aimed to determine the prevalence and characterize the clinical profile of pneumonia among pediatric ALL patients in Urmia, Iran.

Methods: A retrospective cross-sectional study was conducted on children (≤18 years) with ALL admitted to oncology wards of teaching hospitals in Urmia from 2020 to 2023. Pneumonia was defined using modified CDC criteria. Data on demographics, clinical characteristics, microbiology, and outcomes were extracted from medical records. Period prevalence, incidence density, and risk factors were analyzed using appropriate statistical tests.

Results: Of 150 eligible patients, 62 (41.3%) developed at least one episode of pneumonia, yielding a period prevalence of 41.3% (95% CI: 33.5–49.1%). Ninety-eight pneumonia episodes were identified, with an incidence density of 5.23 per 1000 patient-days. Most episodes (67.3%) were clinically diagnosed. Microbiological confirmation (32.7% of episodes) identified bacterial (62.5%), viral (25.0%), and fungal (12.5%) pathogens, with Pseudomonas aeruginosa being most common. Severe neutropenia (ANC <500 cells/µL) (adjusted OR: 4.2, 95% CI: 2.1–8.4; p<0.001) and high-risk ALL (adjusted OR: 2.8, 95% CI: 1.3–6.0; p=0.009) were independent risk factors. Complications included ICU admission (22.4%) and pneumonia-associated mortality (6.1%).

Conclusions: Pneumonia is highly prevalent and severe in pediatric ALL patients in this setting, strongly associated with severe neutropenia and high-risk disease. Findings underscore the need for enhanced surveillance, optimized prophylaxis, and prompt management to mitigate this major infectious complication.