Unilateral absence of the pulmonary artery (UAPA) is a rare congenital cardiovascular malformation with an estimated prevalence of 1 in 200000. There is no gender or race predilection. UAPA is thought to be the result of failure of the fusion between the pulmonary trunk and the sixth aortic arch during embryologic development. The right pulmonary artery is most frequently affected, accounting for two thirds of the cases. Left sided agenesis seems to be more frequently associated with cardiac abnormalities such as tetralogy of Fallot or cardiac septal defects (1).
Clinical presentation of isolated UAPA is divers. It can be asymptomatic until late adulthood, but more often symptoms such as dyspnea, chest pain, decreased exercise tolerance, hemoptysis and recurrent respiratory tract infections are reported. Hemoptysis is caused by large collateral circulations that exposes the venous systems to abnormally elevated pressures. Other complications are pulmonary hypertension, right heart failure and bronchiectasis.
Typical chest radiographic findings are absent hilar shadow, displacement of cardiac and mediastinal shadow, elevation of the diaphragm and contralateral lung hyperinflation.
The definitive diagnosis of UAPA can be made by CT-scan or MRI. Cross-sectional imaging shows the absence of the pulmonary artery with collateral circulation, cardiac and mediastinal displacement, lung volume loss, mosaic parenchymal alterations and bronchiectasis due to recurrent infections. Transthoracic echocardiogram can also be used to establish the diagnosis. Angiography is considered the golden standard but is invasive and is rarely performed unless a surgical intervention is considered.
A remarkable aspect of our case is the presence of advanced asymmetric emphysematous changes in the right lung. Currently, it is assumed that emphysema is the result of an imbalance in protease-antiprotease activity. Cigarette smoking is associated with the induction of proteases, but in our case the emphysema presented mainly in the hypoperfused right lung. A possible explanation could be that hypoperfusion of the right lung prohibits the antiproteases in the blood to reach the proteinases produced locally in the lung, hereby inducing an imbalance (2).
Currently, there is no consensus regarding treatment of patients with isolated UAPA. Treatment options include revascularisation surgery, pneumonectomy or lobectomy and embolization of collateral haemorrhage.
In conclusion, UAPA is an extremely rare congenital disorder and is sometimes asymptomatic until late adulthood, postponing the diagnosis. Multiple imaging modalities are available to establish the definite diagnosis. Our case describes the rare finding of advanced asymmetric emphysematous changes in the affected lung.