8 in 10 people with BHD get lung cysts. Your doctor may also call these cysts “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 in BHD the lower lungs are usually more affected than the upper lungs. BHD lung cysts do not normally affect how well your lungs function. However, it is thought that they may be the cause of lung collapses in BHD.
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 two cm long.