Characteristics of Secondary Malignancy Among Children With Primary Immunodeficiency Disorders in Saudi Arabia

Background Children with primary immunodeficiency disorders (PIDDs) are at an increased risk of developing malignancies due to impaired immune surveillance and genomic instability. In Saudi Arabia, limited data exist regarding the frequency, characteristics, and outcomes of secondary malignancies in this vulnerable population. Therefore, this study aimed to evaluate the clinical features, types of PIDD, associated secondary malignancies, treatment modalities, and outcomes among pediatric patients with PIDD treated at a tertiary care center in Saudi Arabia. Methods This retrospective observational cohort study included 28 pediatric patients diagnosed with both PIDD and malignancy at King Fahad Medical City, Riyadh, between January 2009 and January 2023. Clinical, demographic, and treatment-related data were collected and analyzed using descriptive statistics and Kaplan-Meier survival analysis. Results Among the 1,793 pediatric oncology patients reviewed, 28 (1.56%) were diagnosed with both PIDD and a secondary malignancy. Most patients were male (64.3%) and Saudi nationals (82.1%). Hematologic malignancies were predominant (85.7%), with secondary hemophagocytic lymphohistiocytosis (42.9%) and diffuse large B-cell lymphoma (21.4%) being the most common. Griscelli syndrome (32.1%) and ataxia-telangiectasia (17.9%) were the most frequently observed PIDD. Chemotherapy was administered to 96.4% of patients, with dose adjustments required in 25.9%. Febrile neutropenia was reported in 70.4%, and infections were documented in 75% of cases. Bone marrow transplantation was performed in 39.3% of patients. Progression-free survival was 92.2%, and overall survival was 64.3%, with sepsis accounting for 80% of deaths. Conclusion Children with PIDD are at high risk for developing early-onset, aggressive malignancies, especially hematologic cancers. Despite significant treatment-related complications and infection susceptibility, curative approaches such as chemotherapy and transplantation are feasible. Early identification, individualized treatment, and aggressive infection control are crucial to improving survival outcomes in this high-risk population.