Junctional epidermolysis bullosa (JEB) is a rare moderate-to-severe form of epidermolysis bullosa that affects fewer than one in every one million people. It usually manifests at birth or in early infancy, and blistering can be found over and throughout the body.
What causes JEB?
JEB, a genetic disease, most often results from mutations (in the LAMA3, LAMB3, and LAMC2 genes) that disrupt production the laminin 332 protein, creating a protein that works poorly or doesn’t work at all. Laminin 332 acts to strengthen the skin, connecting its upper layer (epidermis) to lower layers, and holding them together. Because of the defective protein, these skin layers easily come apart, resulting in delicate skin that tears and blisters at the touch.
LAMB3 mutations account for about 70 percent of all junctional epidermolysis bullosa cases.
Mutations in the COL17A1 gene typically cause what is known as the non-Herlitz form of JEB. This gene codes for a protein used to assemble type XVII collagen, molecules that give structure and strength to connective tissues like skin, tendons, and ligaments. The mutations affect the formation of type XVII collagen, and skin that blisters easily.
Types and symptoms
There are two subtypes of JEB:
- Non-Herlitz JEB is the milder form. Blistering may be limited to the hands, elbows, and feet, and often improves as the infant ages. Hairless areas (alopecia), malformed fingernails and toenails, and irregular tooth enamel may also be evident. Serious complications, like breathing difficulties and extensive scarring, are rare, and a normal lifespan is possible.
- Herlitz JEB is severe, and evident at or shortly after birth. Blistering is found across the body, and in the mucosal lining (mucus membranes) of the mouth and digestive tract, including the intestines, affecting a child’s ability to eat and digest food. Chronic malnutrition and stunted growth can result. Blistering in Herlitz JEB patients often leads to scarring which, over time, can result in granulation tissue — red, bumpy skin that is easily damaged and can bleed profusely, increasing the risk of infection, dehydration, and the loss of other essential proteins and minerals. Fused fingers, joint deformities that affect movement, and abnormal fingernail or toenail are also known to affect infants with this form of JEB. It is considered life-threatening, and children born with Herlitz JEB often die in infancy.
Treatment of JEB
Treatment generally consists of avoiding damage to the skin, reducing pain, preventing and treating infections, and ensuring that the patient is not malnourished or dehydrated.
Surgery to widen the esophagus for easier eating and to correct deformities to the joints, feet, and hands is possible.
No cure or treatment that might halt disease progressions exists for JEB, but research is ongoing into such possibilities as gene therapy. Here is one gene therapy success story for a young boy with junctional EB.
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