Mycobacterial infection of a congenital bronchogenic cyst.

Bronchogenic cysts result from an abnormal budding or branching of the tracheobronchial tree. Approximately 30% of the cysts are located in the mediastinum and the remaining 70% in the lung. The cyst may be joined to the tracheobronchial tree by a fistula or by a fibrous band. Pulmonary bronchogenic cysts occur most frequently in the lower lobes, primarily on the right side. They are thin-walled, single or multiple, and lined with respiratory epithelium. The wall consists primarily of fibrous connective tissue and may contain mucous glands, hyaline cartilage, smooth muscle, nerve trunks, and elastic fibres. Bronchial communication with the cyst may be present. Intermittent patency of this communication allows accumulation of various combinations of air, fluid, blood, and purulent material within the cyst. Approximately 15% of patients with bronchogenic cysts in reported series are asymptomatic.'-3 Respiratory symptoms in infants are primarily caused by expansion of the cyst with compression of adjacent tissue causing progressive respiratory distress and death.4 After infancy the symptoms are mainly related to complications including secondary infection, haemorrhage, perforation, and the occasional development of a malignant tumour. We report an asymptomatic patient with evidence of mycobacterial infection within a congenital bronchogenic cyst.