Late Presentation of a Congenital Lung Anomaly Mimicking Unilateral Pulmonary Fibrosis: A Rare Case of Pulmonary Artery Agenesis with Hypoplasia

Congenital lung anomalies (CLAs) are rare developmental abnormalities involving the airways, vasculature, or parenchyma of the lung. They are typically diagnosed in childhood but can present incidentally or symptomatically in adults. Unilateral absence of pulmonary artery (UAPA) with pulmonary hypoplasia with coexisting right aortic arch is an uncommon congenital condition. We report a case of a 63-year-old woman who presented with dyspnea for 2 years, and her clinical examination and imaging findings were suggestive of unilateral pulmonary fibrosis. However, contrast-enhanced computed tomography revealed complete agenesis of the left pulmonary artery, left lung hypoplasia, and a right-sided aortic arch. This case underscores the diagnostic challenge posed by rare congenital anomalies presenting in adulthood. While postinfectious or autoimmune interstitial lung disease was initially suspected, detailed imaging played a crucial role in the correct diagnosis. The extensive cystic and bronchiectatic destruction of the unilateral lung should raise the suspicion of congenital anomalies even in late presentations. This case highlights the importance of considering congenital vascular and parenchymal anomalies in adults with unilateral pulmonary findings. Early and accurate diagnosis can guide appropriate management and prevent unnecessary interventions.