Lung cysts

8 in 10 people with BHD get lung cysts. Your doctor may also call these cysts “blebs” or “bullae”, although BHD lung cysts are usually found in a different area of the lung to common blebs or bullae.

The cysts are sacs of lung tissue that are filled with air. They are usually found on the outside surface of the lung, and the lower lungs are usually more affected than the upper lungs. BHD lung cysts do not normally affect lung function.

The number and size of lung cysts vary from person to person. In one study, the number of cysts per person ranged from 30 to 400, and from a few millimetres to more than 2 cm in diameter.

It is thought that lung cysts may cause collapsed lungs in BHD patients. Lung cysts can burst, releasing air into the space between the lung and the chest wall (the pleural cavity). Over time, air can escape through this gap and build up in the pleural space. When the air pressure is higher in the pleural cavity than in the lung, the lung will collapse. As the amount of air in the pleural cavity increases, more of the lung will collapse, and the worse the symptoms will get.

Please see spontaneous pneumothorax for more information about collapsed lungs.


1. Tobino K, Hirai T, Johkoh T, Kurihara M, Fujimoto K, Tomiyama N, et al. Differentiation between Birt-Hogg-Dubé syndrome and lymphangioleiomyomatosis: Quantitative analysis of pulmonary cysts on computed tomography of the chest in 66 females. Eur J Radiol [Internet]. 2012 Jun [cited 2021 May 11];81(6):1340–6. Available from:

Last Updated: May 2021
Review date: May 2024