Junctional Epidermolysis Bullosa

Junctional epidermolysis bullosa (JEB) is an autosomal-recessive mechanobullous skin disorder that clinically presents as tense blisters on the extremities and trunk with variable involvement of the mucosa and nails. Junctional epidermolysis bullosa can be divided into 3 major subtypes: Herlitz JEB, non-Herlitz JEB, and JEB with pyloric atresia. The subtypes are characterized by the formation of bullae within the lamina lucida. The Herlitz type is characterized by reduced or absent laminin-332, formerly laminin-5, while the non-Herlitz type is caused by a missense mutation, which leads to a reduction of functional laminin-332. Some cases of non-Herlitz JEB are due to complete absence of type XVII collagen. The third subtype, JEB with pyloric atresia, is caused by the genetic mutation that code α6β4 integrin subunits, the main receptor for the ligand laminin-332 beneath the hemidesmosomes. Histology of JEB is remarkable for subepidermal separation with bullae, which usually are without substantial inflammatory infiltration. Electron microscopy reveals disruption in the basement membrane zone with separation through the lamina lucida.