Congenital cystic adenomatoid malformation associated with right aortic arch with mirror image branching and absence of left pulmonary artery in an adult

Background: Congenital cystic adenomatoid malformation is an uncommon developmental anomaly that is diagnosed prenatally or during early childhood and is rare to present in adulthood. Type 2 congenital cystic adenomatoid malformation is often associated with other anomalies such as congenital cardiac anomalies. We present a case of type 2 congenital cystic adenomatoid malformation in an adult male associated with absence of left pulmonary artery and right aortic arch with mirror image branching. To our knowledge, this is the first case report with the combination of all three anomalies. Case presentation: A 33-year-old male presented to the Department of Pulmonary Medicine with high-grade fever, chills and rigor, breathlessness, and productive cough for a duration of one week. He had multiple similar self-limiting episodes in the past which did not require hospitalization. The plain radiograph showed right aortic arch and a small left hilum. CT thorax showed multiple cystic lesions of size 0.5-2.0 cm in the apico-posterior segment of the left upper lobe; anterior, posterior, and lateral segments of the left lower lobe; and the apical segment of the right upper lobe with a maximal cyst wall thickness of 2 mm. Volume of left lung was reduced with trans-thoracic herniation of the medial segment of the right middle lobe; bronchiectatic changes were seen in the apical, anterior, and posterior segments of the right upper lobe; and fibrotic strands were seen in the apical segment of the right lower lobe and the apico-posterior segment of the right upper lobe. Mediastinal window showed right-sided aortic arch with mirror image branching. The pulmonary trunk was seen to continue as the right pulmonary artery with absent left pulmonary artery. Conclusions: Though congenital cystic adenomatoid malformation is a disease of infancy and childhood, it should also be considered in adults presenting with recurrent lower respiratory tract infections and/or pneumothorax. Radiologists must be aware of the types of congenital cystic adenomatous malformation (CCAM) and their associations, as type 2 CCAM has a high association with congenital cardiac disease. Proximal interruption of pulmonary artery should be considered if the pulmonary trunk continues as either right or left pulmonary artery.