Epidermolysis bullosa is usually inherited. Researchers have identified more than a dozen genes involved with skin formation that, if defective, may cause a type of epidermolysis bullosa.

The skin is made up of an outer layer (epidermis) and an underlying layer (dermis). The area where the layers meet is called the basement membrane zone. The type of epidermolysis bullosa you have is defined by where in these layers the blisters form.

The main types of epidermolysis bullosa are:

  • Epidermolysis bullosa simplex. This is the most common form. It usually begins at birth or in early infancy and affects mainly the soles of the feet and the palms.

    In epidermolysis bullosa simplex, the gene that helps produce a fibrous protein (keratin) in the top layer of skin is faulty. The condition causes blistering in the epidermis. The blisters usually don't result in scars with this mild type.

    If you have epidermolysis bullosa simplex, it's likely you inherited a single copy of the defective gene from one of your parents (autosomal dominant inheritance pattern). If one parent has the single faulty gene, each of his or her offspring has a 50 percent chance of having the defect.

  • Junctional epidermolysis bullosa. This type usually is severe and becomes apparent at birth. A baby with this condition may develop a hoarse-sounding cry from continual blistering and scarring of the vocal cords.

    The genes that help form thread-like fibers (fibrils) that attach the epidermis to the basement membrane are faulty. This gene defect causes tissue separation and blistering in this deeper layer of skin.

    If you have junctional epidermolysis bullosa, it's because both your parents carry one copy of the defective gene and passed on the defective gene (autosomal recessive inheritance pattern). Even so, neither parent may show signs or symptoms of the disorder (silent mutation). If both parents carry one faulty gene, each of their offspring has a 25 percent chance of developing the disorder.

  • Dystrophic epidermolysis bullosa. With this type, you may experience mild to severe signs and symptoms. It generally becomes apparent at birth or during early childhood.

    This condition is related to a flaw in the gene that helps produce a type of collagen. If this substance is missing or doesn't function, the layers of the skin won't join properly.

    This type can be either dominant or recessive.

  • Kindler syndrome. This type is rare and usually becomes apparent at birth or soon after.

    This condition is called mixed type because blisters appear across the skin layers. The condition usually improves with time and can disappear. It is the only type that causes patchy discoloring (mottling) of skin exposed to the sun.

    Kindler syndrome is recessive.

Epidermolysis bullosa acquisita is a rare type that isn't inherited. The blisters result from your immune system attacking healthy tissue by mistake. It's similar to another immune system disorder called bullous pemphigoid. It tends to cause blisters on the hands, feet and mucous membranes.

Aug. 22, 2014