Severe Pneumocystis jirovecii Pneumonia in an Apparently Immunocompetent Child Complicated by Acute Respiratory Distress Syndrome and Air Leak Syndrome: A Case Report and Literature Review.

Pneumocystis jirovecii pneumonia (PJP) is an opportunistic fungal infection that predominantly affects immunocompromised individuals. Reports in immunocompetent children are rare. We report the case of a previously healthy 5½‑year‑old Saudi girl who presented with fever, dry cough, and progressive respiratory distress. Her condition rapidly deteriorated, requiring pediatric intensive care admission and mechanical ventilation due to severe acute respiratory distress syndrome. Her course was complicated by pneumothorax, pneumomediastinum, and extensive surgical emphysema. Extensive microbiological investigations were negative except for bronchoalveolar lavage demonstrating Pneumocystis jirovecii using Gomori methenamine silver staining. The patient was treated with intravenous trimethoprim-sulfamethoxazole and supportive intensive care management with gradual clinical recovery. Immunological evaluation, including lymphocyte subsets, immunoglobulin levels, complement levels, vaccine antibody responses, and whole‑exome sequencing, revealed no evidence of primary or secondary immunodeficiency. Long‑term follow‑up for more than 10 years showed no recurrent severe infections. This case highlights that PJP may rarely occur in immunocompetent children and can present with life‑threatening respiratory failure. Awareness of this possibility is important in severe unexplained pneumonia.