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Junctional epidermolysis bullosa, non-Herlitz type
Junctional epidermolysis bullosa, non-Herlitz (JEB-nH) is a subtype of junctional epidermolysis bullosa (JEB, see this term) characterized by the presence of skin and mucosal blistering, nail dystrophy or nail absence and enamel hypoplasia.
Exact prevalence data are not available but the US EB registry indicates that prevalence of all other variants of JEB is 5 times that of JEB-Herlitz (about 1/14,000,000) with an estimated value of about 1/2,700,000.
Postinflammatory hypopigmentation or dyspigmentation may be striking in some JEB-nH patients. A generalized subtype with atrophic scarring and more extensive extracutaneous involvement has been described (Junctional epidermolysis bullosa, generalized non-Herlitz type; see this term) as well as a milder localized subtype (Junctional epidermolysis bullosa, localized non-Herlitz type; see this term).
JEB-nH is caused by mutations in the COL17A1 (10q24.3) and LAMA3 (18q11.2), LAMB3 (1q32) and LAMC2 (1q25-q31) genes.
In addition to the finding of a cleavage plane located within the lamina lucida of the cutaneous basement membrane zone, a strongly reduced immunofluorescence staining for laminin-332 or a negative/reduced labeling for collagen XVII (BP180) is typical of JEB-nH. Genetic testing can be required to distinguish between JEB-H, due to null mutations on both alleles of one of the three genes encoding laminin-332, and JEB-nH due to laminin-332 deficiency where a different type of mutation (e.g. missense, splice-site) is found on at least one allele of the mutated gene.
The condition follows an autosomal recessive pattern of inheritance.
Although JEB-nH is less severe than JEB-H, sepsis, failure to thrive and respiratory failure can lead to death in infancy and childhood. According to data from the U.S. National EB Registry, the cumulative risk of upper airway occlusion in JEB-nH (13% by age 9) is lower than that observed in JEB-H although the risk of death among JEB-nH patients with this complication is essentially the same.