Junctional Epidermolysis Bullosa
Junctional epidermolysis bullosa (JEB) is a form of inherited epidermolysis bullosa (see this term) characterized by involvement of the skin and mucous membranes, and is defined by the formation of blistering lesions between the epidermis and the dermis at the lamina lucida level of the cutaneous basement membrane zone and by healing of lesions with atrophy and/or exuberant granulation tissue formation.
Epidemiology
JEB is the less common, but frequently early lethal form of EB. Incidence data from the U.S. and Italian EB registries indicate 1/450,000 and 1/260,000 live births, respectively.
Clinical description
Onset is usually at birth with the exception of late-onset JEB. Several JEB subtypes have been described based on clinical features. All subtypes are characterized by the presence of enamel hypoplasia manifesting as localized or more extensive thimble-like pitting of some or all of the tooth surfaces. Blistering is usually associated with atrophic scarring or with exuberant granulation tissue formation and nail dystrophy. Additional skin findings may include congenital aplasia cutis congenita (see this term) and progressive hair loss. Mucosal involvement is constant, although of variable severity, and can affect the gastrointestinal, respiratory and genitourinary tracts and the eyes. Pyloric atresia is the hallmark of the JEB with pyloric atresia subtype (see this term). JEB is divided in two major subtypes: the more severe JEB-Herlitz form and the JEB-other subtype which in turn comprises six variants, the last 3 of which are very rare (JEB, non Herlitz, generalized; JEB, non-Herlitz, localized; JEB with pyloric atresia; JEB inversa; late-onset JEB; LOC syndrome (see these terms)).
Etiology
JEB is caused by mutations in various genes, including COL17A1, ITGA6, ITGB4, LAMA3, LAMB3 and LAMC2.
Diagnostic methods
Diagnosis is based on determination of the level within which blisters develop on skin biopsy samples following minor traction to the skin. The recommended techniques are immunofluorescence antigen mapping and transmission electron microscopy. In JEB, the blister cleavage plane is localized within the lamina lucida of the cutaneous basement membrane zone. Subtypes are then defined on the basis of immunofluorescence and electron microscopic findings, and clinical presentation. Genetic testing is possible and for some JEB subtypes it is necessary to confirm the diagnosis.
Differential diagnosis
Diagnosis is usually straightforward with little need for extensive differential diagnosis. However, in the neonatal period, in utero Herpes simplex infection may need to be considered, especially if there is no family history of blistering disease or if the clinical findings are very atypical for EB. The differential diagnosis in neonates may include inherited or acquired skin disorders with a similar presentation.
Antenatal diagnosis
Prenatal diagnosis can be performed by DNA mutational analysis.
Genetic counseling
JEB is inherited in an autosomal recessive manner. Genetic counseling should be performed either by a medical geneticist or a dermatologist who has considerable experience with EB.
Management and treatment
Patients affected by most JEB forms require hospitalization in neonatal intensive care because of the severity skin lesions and extracutaneous manifestations, to monitor the water-electrolyte balance, and for treatment of failure to thrive, anemia, infectious and respiratory complications, etc. Pain management is also extremely important in these patients and often requires opioids. Subsequently, patient management should involve a multidisciplinary team, to ensure coordinated care. Skin management is based on the avoidance of blistering by meticulous protective padding of the skin, avoidance of trauma in daily life, lancing and draining of new blisters, and prevention of secondary infection by careful wound care.
Prognosis
Patients with JEB, particularly those with JEB-H, JEB-PA and LOC syndrome, are at major risk of death during the first few years of life.