Birt-Hogg Dubé (BHD) is characterized by skin lesions, kidney tumors, and pulmonary cysts that may be associated with pneumothorax.
It is designated with the name of the three Canadian physicians who described the syndrome in 1977. The prevalence is estimated at 1/200,000 rare pathological condition, but the exact incidence is unknown.
The BHD syndrome is transmitted in an autosomal dominant manner. It has located a potentially responsible gene on locus 17p11.2: FLCN. This gene encodes folliculin and although their function is still unknown, is believed to be a component of the mTOR pathway, which is involved in the development of kidney tumors and possibly in the development of other associated injuries.
Renal tumors in patients with BHD oncocytomas range from benign to renal carcinomas, including subtypes: chromophobe, clear cell or papillary. Typical cutaneous lesions are called fibrofolliculomas, characterized by a circumscribed proliferation of fibroblast collagen and twisted around the hair follicles from which protrude basaloid cells in the stroma surrounding fibromucinoso. Other features include skin abnormalities trichodiscomas and skin tags. Dermatological manifestations of BHD syndrome usually develop during the third and fourth decade of life and persist indefinitely. Moreover, cutaneous manifestations usually precede the associated renal tumors. Pulmonary cysts are characterized by cystic dilation of the alveolar spaces, with a diameter ranging from microscopic to several millimeters. The rupture of cysts by the pressure of inspiration, can lead to pneumothorax.
The diagnosis is based on clinical and histological data confirming the presence of trichodiscomas, perifollicular and fibrofolliculomas fibroids. The diagnosis can be confirmed by detection of the mutation in the BHD (FLCN) gene.
The differential diagnosis of multiple papules of BHD syndrome depends on the origin of the skin lesions: epithelial, mesodermal or different origin.
Patients suffering from BHD syndrome and their families should receive genetic counseling and, if possible, a genetic test. Monitoring of patients and management of pulmonary, renal or gastrointestinal manifestations is necessary. The prognosis depends on the severity of visceral damages involved and the type of renal tumor.