Epidermolysis bullosa (EB) refers to a group of rare diseases that cause the skin to be very fragile, tearing and blistering easily when touched. There are four main types of EB, one of which is dystrophic epidermolysis bullosa (DEB), which affects approximately 3.3 individuals per million people.
What causes DEB?
All types of DEB are caused by mutations in the COL7A1 gene, which encodes for a portion of the type VII collagen protein. Collagen proteins give structure and support to tissues and organs, including the skin. Type VII collagen connects the different layers of the skin, anchoring them to each other. When this collagen is faulty or absent, these connections are very fragile and even small movements of the skin can cause separation of the layers, leading to the formation of blisters, and scar tissue as the blisters heal.
DEB is categorized as severe or mild. Severe DEB is caused by the loss of type VII collagen, while the mild form of the disease is caused by mutations that reduce the amount of type VII collagen but allow some functional protein to be produced.
How is DEB inherited?
Patients with recessive DEB must have inherited two copies of disease-causing mutations — one from each parent who likely do not show signs of the disease. If a person with recessive DEB has children with someone without any disease-causing mutations, their children will be carriers of the disease. Carriers have a copy of a disease-causing mutation, but are unlikely to develop any symptoms.
If a patient with recessive DEB has children with a carrier of the disease, their children will have a 50% chance of inheriting two copies of the disease-causing mutation and developing DEB. The children will also have a 50% chance of being carriers.
If two carriers of recessive DEB have children together, their children have a 25% chance of inheriting one copy of the disease-causing gene from each parent and developing the disease. They also have a 50% chance of being carriers like their parents and a 25% chance of not inheriting any faulty gene.
Dominant DEB develops if a person inherits a single copy of the disease-causing mutation that’s sufficient to cause the disorder, which occurs in about 70% of cases. The remaining 30% of dominant DEB occur from new mutations. If a patient with dominant DEB has children with a person without the disease, their children will have a 50% chance of inheriting a disease-causing mutation and developing the disease, and a 50% chance of not having the disease.
What are the symptoms of DEB?
Patients with DEB have skin that is fragile and blisters easily in response to minor injuries, or even rubbing or scratching. The severity of the symptoms varies widely among individuals. In mild cases, the blistering may occur on the extremities such as the hands, feet, knees, and elbows. Severe cases can mean widespread blistering that can cause scarring, vision loss, and severe medical problems.
The symptoms may be present from birth. In severe cases, scarring in the mouth and throat can make it difficult for babies to swallow, which can lead to malnutrition. In some cases, scarring may cause fusion of the fingers and toes, loss of fingernails, and inflammation in the eyes that can cause blindness.
How is DEB diagnosed?
A physical examination of blisters or skin lesions can be used to diagnose DEB, followed by a skin biopsy. To confirm a diagnosis of DEB, the physician will order a genetic test. For the test, a small sample of blood will be drawn from the patient, and sent to a laboratory to be examined for any mutations in the COL7A1 gene. Genetic test results may take four to six weeks to become available. Based on the results, the doctor may ask for additional tests to check for any complications that are common in DEB, such as a cancer screen.
How is DEB treated?
With no current cure for any type of EB, a few treatments are available to reduce complications. Most treatments are preventive and focus on reducing the chance of blisters by protecting skin from damage and treating blisters promptly to prevent infections or further damage.
Last updated: Feb. 12, 2020
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