It usually manifests at birth or in early infancy, and blistering can be found over large areas of the body. Blisters occur within the basement membrane zone — a layer between the epidermis (top skin layer) and the dermis, the skin’s lower layer.
JEB, a genetic disease, often results from mutations in the LAMA3, LAMB3, and LAMC2 genes that disrupt production of laminin 332, creating a protein that works poorly or does not work at all. Laminin 332 acts to strengthen the skin, holding skin layers together. Because of the defective protein, these skin layers easily come apart, resulting in delicate skin that tears and blisters easily.
LAMB3 mutations account for about 70% of all JEB cases.
Mutations in the COL17A1 gene typically cause what is known as the generalized intermediate form of JEB. This gene codes for a protein used to assemble type XVII collagen. Collectively, collagens give structure and strength to connective tissues such as the skin, tendons, and ligaments. These mutations affect the formation of type XVII collagen in the skin, causing it to blister due to friction or other minor trauma.
JEB is inherited in an autosomal recessive pattern, meaning that both parents must pass down a defective copy of the disease-causing gene.
Subtypes and symptoms
JEB has two main forms:
Non-generalized severe JEB
Non-generalized severe JEB is the milder form. Blistering may be limited to the hands, elbows, and feet, and often improves in infancy. Hair loss, malformed fingernails and toenails, and irregular tooth enamel may also be evident. Serious complications, like breathing difficulties and other severe complications, are rare, and a normal lifespan is possible.
Generalized severe JEB
Generalized severe JEB is evident at or shortly after birth. Blistering is widespread in the body, affecting the mucosal lining of the mouth and digestive tract, and the ability to eat and digest food. Chronic malnutrition and stunted growth can result.
Blistering in these patients often leads to scarring and red, bumpy skin that is easily damaged and can bleed extensively, increasing the risk of infection, dehydration, and the loss of essential proteins and minerals. Fused fingers, joint deformities that affect movement, abnormal fingernails or toenails, and breathing difficulties are also known to affect infants with this form of JEB. Children born with generalized severe JEB usually have a poor life expectancy.
Other forms of JEB include:
- localized JEB — characterized by neonatal onset of localized blistering mainly confined to hands, feet, lower legs, and face
- JEB with pyloric atresia — generalized blistering at birth and blockage of the lower part of the stomach
- JEB inversa — usually with severe blistering and symptoms such as nail distortion or discoloration, thin or absent enamel, and oral, esophageal and vaginal blisters
- late-onset JEB — blisters around the nails start in childhood or adolescence, then affect other areas but heal with scars
- JEB with interstitial lung disease and nephrotic syndrome — a life-threatening disorder that develops in the first months of life, and presents with respiratory distress and leads to severe interstitial lung disease (associated with scarring) and renal failure.
Treatment generally consists of avoiding damage to the skin and using protective padding, draining new blisters, reducing pain, preventing and treating infections, and ensuring that the patient is not malnourished or dehydrated.
Surgery can widen the esophagus for easier eating and correct deformities in the joints, feet, and hands.
Treating JEB typically involves a multidisciplinary team, which can include a dermatologist, dentist, dietitian, physiotherapist, play specialist — who uses playful activities to help improve a child’s physical and psychological well-being — and specialist nurse.
Last updated: July 14, 2021
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