A 29-year-old male presented to the emergency room with sudden onset of dyspnoea and cough that started while travelling in a hilly region. He reported a history of asthma since childhood, requiring the intermittent use of inhalers. There were no other co-morbidities, history of prior tuberculosis or prior severe exacerbations of asthma. He rapidly went into respiratory failure, requiring intubation and high FiO2. Chest radiographs revealed left-sided pneumonia and an unexplained right lung volume loss, for which he was treated with antibiotics. He recovered within 3 days and was discharged. He returned for follow-up to understand the cause for his sudden and severe respiratory deterioration at high altitude.
Physical examination was unremarkable apart from the right lung volume loss and a few scattered crepitations on the right side. Laboratory reports showed normal haemogram, and normal renal and liver function tests. D-dimer screening and venous Doppler of both lower limbs were negative for deep vein thrombosis. Echocardiogram did not show evidence of elevated pulmonary artery (PA) pressures.
All prior serial chest radiographs demonstrated a consistent right lung volume loss with transmediastinal herniation of the left lung. High-resolution CT chest, performed the previous year, confirmed right lung volume loss and revealed a subtle reticulation that had been attributed to tubercular sequelae. However, the patient did not know of any prior tubercular illness or antitubercular therapy. He did, however, report that, while in utero, his mother had unsuccessfully attempted to medically terminate the pregnancy.
The current chest radiograph demonstrated a small volume right lung, mild elevation of the right hemidiaphragm, ipsilateral mediastinal shift, absence of the right PA, dilated left PA and a hyperinflated left lung that had herniated to the right side, as indicated by a displaced anterior junction line. Within the small right lung, there was a subtle reticulation, most obvious in the periphery of the upper zone. The intrapulmonary vasculature of the left lung was normal (Figure 1).
Contrast-enhanced CT (CECT) of the chest revealed dilatation of the left PA and its divisions with complete absence of the mediastinal segment of the right PA (Figures 2 and 3). In addition, branches of the dilated intercostal collateral arteries were present in the right epicardial fat (Figure 2b) and a dilated right internal mammary artery was identified in the anterior chest wall (Figure 2a,b). The small right lung demonstrated fine reticular opacification consistent with transpleural collateral arteries (Figure 4a,b). Although the right lung was small, the bronchial airway branching pattern was normal with no evidence of bronchiectasis, fibrosis or cavitation. Herniation of the hyperinflated left lung into the right hemithorax was evident.