Pulmonary tuberculosis with unusual cystic change in an immunocompromised host

We present a rare case of upper zone cystic change of the lung with dissemi nated tuberculosis of a non-smoking 30-year-old immunocompromised male. He suffered from repeated pneumothorax. The basic pathological feature of vide o-assisted thoracoscopic lung biopsy revealed granulomatous involvement in the respiratory bronchioles with poorly developed epithelioid cells and dis ruption of elastic fibers. Electron microscopy demonstrated a decrease in e lastic fibers and disruption of the epithelial basement membrane of the res piratory bronchiole and no Langerhans cells in the lesion. Autopsy of the l ung revealed centroacinar distribution of multiple cystic lesions in the bi lateral upper lobe. Almost all cystic walls showed loss of elastic fibers a nd cysts frequently involved the respiratory and terminal bronchioles, alve olar ducts and, occasionally, alveoli. Some larger cystic lesions revealed communication to the bronchi. The cystic changes in this case of pulmonary tuberculosis may be caused by a check-valve mechanism due to granulomatous involvement of the bronchioles and also by excavation of caseous necrotic m aterial by draining bronchi.