A rare case of multiple fibro-folliculomas and lung cysts: Possible Birt-Hogg-Dube syndrome

Birt-Hogg-Dubè (BHD) syndrome, also called HornsteinKnickenberg syndrome, was first described in 1977 (1). It is a rare autosomal dominant disease that is characterized by multiple fibro-folliculomas on the skin, lung cysts that predispose to spontaneous pneumothorax, and increased risk of renal cancer (2,3). BHD syndrome is caused by loss-of-function mutation in the folliculin, also known as FLCN gene found on chromosome 17p12-q11.2 that encodes for the protein folliculin. Folliculin is expressed in a variety of tissues including the skin, lungs and kidneys. The prevalence of BHD is about 1/200,000 although it is believed that this has been underestimated because of the wide phenotypic interfamilial variability. Less than 300 families have been described to date in the literature and the incidence has been the same for both sexes (4).