Junctional Epidermolysis Bullosa (JEB)
Junctional Epidermolysis Bullosa (JEB) is usually severe type of the disorder generally becomes apparent at birth. In Junctional Epidermolysis Bullosa (JEB), the mutated genes are involved in the formation of thread-like fibers (hemidesmosomes) whic attach the epidermis to the basement membrane. This gene defect causes tissue separation and blistering in the basement membrane zone (BMZ).
Junctional Epidermolysis Bullosa (JEB) has autosomal recessive inheritance pattern in which both parents carrying one copy of the diseased gene and passing on the mutated gene, although neither parent may clinically have the disorder (silent mutation).
If both parents carry one faulty gene, there's a 25% chance each of their offspring will inherit two mutated genes — one from each parent — and develop the disorder.
Primary subtypes include a lethal subtype termed Herlitz or junctional epidermolysis bullosa letalis, a nonlethal subtype termed junctional epidermolysis bullosa mitis and a generalized benign type termed generalized atrophic benign epidermolysis bullosa.
Lethal junctional epidermolysis bullosa
The Herlitz or letalis form of junctional epidermolysis bullosa is characterized by generalized blistering at birth and arises from an absence or a severe defect in expression of the anchoring filament glycoprotein laminin 5. Patients with lethal forms of junctional epidermolysis bullosa show characteristic periorificial erosions around the mouth, eyes and nares, often accompanied by significant hypertrophic granulation tissue. Multisystemic involvement of the corneal, conjunctival, tracheobronchial, oral, pharyngeal, esophageal, rectal, and genitourinary mucosae is present. Internal complications of the disease include a hoarse cry, cough, and other respiratory difficulties. Patients with Herlitz junctional epidermolysis bullosa are at increased risk for death from sepsis or other complications secondary to the profound epithelial disadhesion and usually they do not survive past infancy.
Junctional epidermolysis bullosa, Herlitz subtype.
This severe disease is characterized by generalized intralamina lucida blistering at birth, significant internal involvement, and a poor prognosis.
Nonlethal junctional epidermolysis bullosa
Patients with junctional epidermolysis bullosa manifesting generalized blistering who survive infancy and clinically improve with age have junctional epidermolysis bullosa mitis. Usually, these patients do not present with the same type of hoarse cry or other significant respiratory symptoms as do patients with the Herlitz form. Instead, scalp, nail, and tooth abnormalities increasingly may become apparent. Periorificial erosions and hypertrophic granulation tissue can be present. Mucous membranes often are affected by erosions, resulting in strictures. Some patients with junctional epidermolysis bullosa mitis can present with blistering localized to the intertriginous regions.
Generalized atrophic benign epidermolysis bullosa
This is a relatively mild subtype characterized by generalized cutaneous blistering and presenting at birth. Blistering activity is worsened by increased ambient temperature, and blisters heal with a distinctive atrophic appearance. Extracutaneous involvement is rare, with the exception of teeth. Hypoplastic enamel formation results in significant tooth decay. Nail dystrophies and alopecia are other common clinical manifestations. Individuals with generalized atrophic benign epidermolysis bullosa have the potential to bear children and have a typical life expectancy. It should be noted that generalized atrophic benign epidermolysis bullosa is lumped together with nonlethal junctional epidermolysis bullosa in the newest epidermolysis bullosa classification consensus; however, it is clear that these 2 diseases are quite distinct clinically.