Background: Pulmonary agenesis is a rare congenital anomaly characterized by the complete or partial absence of lung tissue, bronchus, and pulmonary vasculature. Advancements in prenatal imaging have improved early detection; however, some cases may still go undiagnosed until after birth and can be discovered fortuitously. Case Presentation: We present a case of a two-month-old male infant with an uneventful perinatal history who presented with respiratory distress initially diagnosed as bronchiolitis. Imaging revealed complete absence of the left lung, main bronchus, and vasculature, with compensatory hyperinflation of the right lung. Based on these findings, a diagnosis of left pulmonary agenesis was made. The infant improved with symptomatic treatment for bronchiolitis and did not require oxygen. Further investigations found no associated congenital anomalies. Conclusion: This case emphasizes the diagnostic challenges of pulmonary agenesis in neonates, the limitations of prenatal screening, and the importance of comprehensive evaluation. In isolated cases without additional malformations, prognosis is favorable, and conservative management with follow-up is often sufficient.
