Birt-Hogg-Dube Syndrome

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What is Birt-Hogg-Dube syndrome?

Birt-Hogg-Dube syndrome is a rare disorder that affects the skin and lungs and increases the risk of certain types of tumors. The condition is characterized by multiple noncancerous (benign) skin tumors, particularly on the face, neck, and upper chest. These growths typically first appear in a person's twenties or thirties and become larger and more numerous over time. Affected individuals also have a higher chance of developing cysts in the lungs and an abnormal accumulation of air in the chest cavity (pneumothorax) that may result in the collapse of a lung. Additionally, people with Birt-Hogg-Dube syndrome have an increased risk of developing cancerous or noncancerous kidney tumors and possibly tumors in other organs and tissues.

How common is Birt-Hogg-Dube syndrome?

Birt-Hogg-Dube syndrome is very rare; the exact incidence is unknown. This condition has been reported in more than 60 families.

What genes are related to Birt-Hogg-Dube syndrome?

Mutations in the FLCN gene cause Birt-Hogg-Dube syndrome.

The FLCN gene provides instructions for making a protein called folliculin. The normal function of this protein is unknown, but researchers believe that it may act as a tumor suppressor. Tumor suppressors prevent cells from growing and dividing too rapidly or in an uncontrolled way. Mutations in the FLCN gene may interfere with the ability of folliculin to restrain cell growth and division, leading to the formation of noncancerous and cancerous tumors. Researchers have not determined how FLCN mutations increase the risk of lung abnormalities, such as a pneumothorax.

How do people inherit Birt-Hogg-Dube syndrome?

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In some cases, an affected person inherits the mutation from one affected parent. Other cases may result from new mutations in the gene and occur in people with no history of the disorder in their family.

Researchers believe that two copies (instead of one copy) of the FLCN gene must be altered for a person to develop the kidney tumors often seen in Birt-Hogg-Dube syndrome. People with this condition are born with one mutated copy of the FLCN gene in each cell. Then, during their lifetime, the other copy of the gene is mutated in kidney cells. These genetic changes disable both copies of the FLCN gene, which allows the cells to divide uncontrollably and form tumors.

Source: National Institutes of Health

Research from National Cancer Institute broadens understanding of pneumothorax risk factors

"BHD mutation data were used for genotype-pulmonary associations. We examined the relationship of pneumothorax with categorical parameters (sex, smoking history, and lung cysts) and continuous parameters (number of cysts, lung cyst volume, and largest cyst diameter and volume). Logistic regression analyses were used to identify the risk factors associated with pneumothorax. Twenty-four percent (48/198) of patients with BHDS had a history of pneumothorax. The presence of lung cysts was significantly associated with pneumothorax (p=0.006). Total lung cyst volume, largest cyst diameter and volume, and every parameter related to the number of lung cysts were significantly associated (p <0.0001) with pneumothorax. A logistic regression analysis showed that only the total number of cysts in the right parenchymal lower lobe and the total number of cysts located on the pleural surface in the right middle lobe were needed to classify a patient as to whether or not he or she was likely to have a pneumothorax. Exon location of the BHD mutation was associated with the numbers of cysts (p=0.0002)," wrote J.R. Toro and colleagues, National Cancer Institute.

The researchers concluded: "This study indicates that patients with BHDS have a significant association between lung cysts and spontaneous pneumothorax."

Toro and colleagues published their study in American Journal of Respiratory and Critical Care Medicine (Lung cysts, spontaneous pneumothorax, and genetic associations in 89 families with Birt-Hogg-Dubé syndrome. American Journal of Respiratory and Critical Care Medicine, 2007;175(10):1044-53).

Additional information can be obtained by contacting J.R. Toro, Genetic Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD 20892-7231 USA.

The publisher of the American Journal of Respiratory and Critical Care Medicine can be contacted at: American Thoracic Society, 1740 Broadway, New York, NY 10019-4374, USA.

Keywords: United States, Rockville, Pneumothorax Risk Factors, Critical Care, Cysts, Genetics, Genotyping, Pneumothorax.

This article was prepared by Disease Prevention Week editors from staff and other reports. Copyright 2007, Disease Prevention Week via NewsRx.com.