Unilateral Acute Respiratory Distress Syndrome with Contralateral Pulmonary Artery Agenesis: A Rare Scenario

Unilateral pulmonary artery agenesis (UPAA) is a rare condition where the patient may remain asymptomatic for a long period till adulthood. Presentation may be in the form of dyspnea, cough, hemoptysis, decreased exercise tolerance, and recurrent respiratory tract infections. Ventilation–perfusion mismatch and excessive blood flow to the normal lung may eventually lead to unilateral acute respiratory distress syndrome (ARDS). We present a case of a 40-year-old gentleman with nonresolving pneumonia who was diagnosed to have unilateral ARDS due to UPAA. Even though ARDS involves bilateral lung, unilateral ARDS which does not show resolution with lung protective strategies should always raise the suspicion of a rare disease like UPAA among clinicians. To date, there is no specific prescribed treatment for UPAA.