Dominant Dystrophic Epidermolysis Bullosa

Dominant dystrophic epidermolysis bullosa (DDEB) is a type of epidermolysis bullosa (EB), which is a group of rare inherited conditions in which the skin blisters extremely easily. DDEB is one of the milder forms of EB, although the severity is variable. Blisters may be present a ...

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Dominant dystrophic epidermolysis bullosa (DDEB) is caused by mutations in the COL7A1 gene. The COL7A1 gene provides instructions for making a protein that is used to assemble type VII collagen. Collagen gives structure and strength to connective tissues, such as skin, tendons, and ligaments, throughout the body.

Type VII collagen plays an important role in strengthening and stabilizing the skin. It is the main component of structures called anchoring fibrils, which anchor the top layer of skin, called the epidermis, to an underlying layer called the dermis.

COL7A1 mutations alter the structure or disrupt the production of type VII collagen, which impairs its ability to help connect the epidermis to the dermis. When type VII collagen is abnormal or missing, friction or other minor trauma can cause the two skin layers to separate. This separation leads to the formation of blisters, which can cause extensive scarring as they heal.

A diagram of the skin structure including the area of skin implicated in DDEB is provided by the National Institute of Arthritis and Musculoskeletal and Skin Diseases. Click on the link for more. 

Dominant dystrophic epidermolysis bullosa (DDEB) is consivered to be a more mild form of dystrophic epidermolysis bullosa (DEB). Blistering is often limited to the hands, feet, knees, and elbows. Blistering may be relatively benign, but still heals with scarring and milia. Dystrophic nails, especially toenails, are common and loss of nails may occur. In the mildest forms, dystrophic nails may be the only characteristic noted. Blistering in DDEB often improves somewhat with age.

Dominant dystrophic epidermolysis bullosa (DDEB) has an autosomal dominant pattern of inheritance. Autosomal dominant inheritance means that one copy of the gene with the mutation in each cell is sufficient to cause the disorder. About 70 percent of individuals with DDEB have inherited a COL7A1 mutation from an affected parent. The remaining 30 percent have the condition as a result of a new (de novo) mutation in the COL7A1 gene. These cases occur in people with no history of the disorder in their family. Regardless of whether an individual with an autosomal dominant condition has inherited the mutation or has a new mutation, each child of the affected individual has a 50% (1 in 2) chance of also having the condition, and a 50% chance of not having the condition.