Skin<unk>  affects the skin and increases the risk of tumors in the kidneys and lungs. The condition is characterized by multiple noncancerous, dome-shaped tumors of the hair follicles (fibrofolliculomas), particularly on the face, neck, and more rarely, the upper chest. The fibrofolliculomas are generally described as having an opaque white color or a yellowish tone and have a waxy, smooth texture. The tumors are always found on and around the nose and on and behind the outer ear. Typically, they first appear in a person's 20s or 30s, and are found in more than 80% of people with the syndrome above the age of 40. The tumors become larger and more numerous over time. Tumors differ between individuals; they may appear merged in plaques, look similar to a comedo with a plug of keratin, or include epidermoid cysts. A large number of tumors on the face can be associated with hyperseborrhea (abnormally elevated sebum production). The presence of fibrofolliculomas on a person's face can cause significant psychological distress. Other tumors can include trichodiscomas (tumors of the hair disc, which may be identical to fibrofolliculomas), angiofibromas, and perifollicular fibromas. However, angiofibromas are more common in tuberous sclerosis. Along with the tumors, other skin conditions are seen in people with<unk> . About 40% of people or families with the disease have papules in their mouths, which can be located on the cheeks (buccal mucosa), tongue, gums, or lips. Either white or mucosa-colored, they are discrete, small, and soft, and consist of fibrous tissue covered in thickened epithelium. Collagenomas of the skin are also found in some families. Many people with BHD have skin lesions that appear to be acrochordons (skin tags), but may instead be fibrofolliculomas. These lesions are usually found in the armpit, on the eyelids, and in folds of skin. Not all individuals develop the facial tumors; some families with the mutation that causes BHD develop only kidney tumors or spontaneous pneumothorax. Kidneys An H&E stain of tissue from a chromophobe renal cell carcinoma, the second-most common cancer associated with BHD People over 20 years of age with BHD have an increased risk of developing slow-growing kidney tumors (chromophobe renal carcinoma and renal oncocytoma, respectively), kidney cysts, and possibly tumors in other organs and tissues. These tumors often occur in both kidneys and in multiple locations in each kidney. The average number of kidney tumors found in a person with BHD is 5.3, though up to 28 tumors have been found. Hybrid oncocytoma/chromophobe carcinoma, found in 50% of cases, is the most commonly found cancer, followed by chromophobe renal carcinoma, clear cell renal carcinoma, renal oncocytoma, and papillary renal cell carcinoma. People over 40 years old and men are more likely to develop kidney tumors, which are diagnosed at a median age of 48. Kidney cancer associated with BHD have been diagnosed in people at ages as young as 20. In general, people with this syndrome are at roughly at seven times the risk of kidney cancer compared to the unaffected population. Estimates of the incidence among people with the disease range from 14–34%. Rarely, it is associated with clear cell renal cell carcinoma and papillary renal cell carcinoma. If it develops in someone with BHD, renal cell carcinoma occurs later in life and has a poor prognosis. Though the types of tumors typically associated with BHD are considered less aggressive, cases of advanced or metastatic kidney cancer have been observed in people with the syndrome. Both benign and cancerous tumors can reduce kidney function over time as they grow larger. Lungs Along with fibrofolliculomas and kidney tumors, affected individuals frequently develop cysts (blebs or bullae) in the subpleural lung base or intraparenchymal space that may rupture and cause an abnormal collection of air in the chest cavity (pneumothorax), which could result in the collapse of a lung. The cysts do not cause other symptoms and lung function is usually normal. More than 83% of people with BHD have cysts, but the syndrome does not cause conditions like progressive chronic obstructive pulmonary disease or generalized respiratory failure, though it does cause emphysema. Spontaneous, sometimes recurrent, pneumothorax occurs far more often and at a younger age with BHD than in the unaffected population. Around 24% of people with the disease suffer at least one spontaneous pneumothorax, 30 times the occurrence in unaffected people. Though pneumothorax caused by BHD often occurs in middle age, at a median age of 38, 17% of affected people have a spontaneous pneumothorax before turning 40. Pneumothoraces have been seen in people as young as 7 and 16 years of age. Some families have a form of BHD that only affects the lungs. Other organs Thyroid nodules have been associated with the<unk> –Hogg–Dubé phenotype, present in 65% of individuals and 90% of families with the syndrome. However, a connection between BHD and thyroid cancer has not been substantiated. Other conditions have been reported to be associated, but may not be caused by the mutation in FLCN or may not be related at all. These include multinodular goiter, medullary thyroid carcinoma, parotid oncocytoma, colonic polyposis, connective tissue nevus, lipomas, angiolipomas, parathyroid adenomas, flecked chorioretinopathy, neurothekeoma, meningiomas, angiofibromas of the face, trichoblastomas, cutaneous focal mucinosis, cutaneous leiomyoma, breast cancer, tonsillar cancer, colorectal cancer, sarcoma of the leg, lung cancer, melanoma, dermatofibrosarcoma protuberans, basal cell carcinoma, cutaneous leiomyosarcoma, and squamous cell carcinoma.
Birt–Hogg–Dubé syndrome
Johnson–McMillin syndrome
Fox–Fordyce disease
Cruveilhier–Baumgarten disease
Yemenite deaf-blind hypopigmentation syndrome
Beare–Stevenson cutis gyrata syndrome
Sézary disease
Ardalan–Shoja–Kiuru syndrome