Birt-Hogg-Dubé Syndrome

What is Birt-Hogg-Dubé syndrome?

Birt-Hogg-Dubé syndrome is a rare disorder that affects the skin and lungs and increases the risk of certain types of tumours. The condition is characterised by multiple noncancerous (benign) skin tumours, 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-Dubé syndrome have an increased risk of developing cancerous or noncancerous kidney tumours and possibly tumours in other organs and tissues.

How common is Birt-Hogg-Dubé syndrome?

Birt-Hogg-Dubé 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-Dubé syndrome?

Mutations in the FLCN gene cause Birt-Hogg-Dubé 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 tumour suppressor. tumour 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 tumours. Researchers have not determined how FLCN mutations increase the risk of lung abnormalities, such as a pneumothorax.

How do people inherit Birt-Hogg-Dubé 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 tumours often seen in Birt-Hogg-Dubé 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 tumours.

What other names do people use for Birt-Hogg-Dubé syndrome?

• BHD
• Fibrofolliculomas with trichodiscomas and acrochordons
• Hornstein-Knickenberg syndrome