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Epidermolysis bullosa (EB) defines a group of rare inherited mechanobullous skin disorders that are characterized by skin fragility and bullae formation. There are three forms of the disease: EB simplex, junctional EB, and dystrophic EB with over 20 different phenotypes representing mutations in the genes of at least 7 structural proteins of the skin (in the epidermis, dermal—epidermal junction, or upper papillary dermis).

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Insight

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Melanocytic nevi in children with recurrent blistering disorders may appear clinically atypical (large and dark with irregular borders) while having reassuring histological patterns.

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Classification

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Inherited EB can be classified based on phenotype and genotype, subdividing EB into types and subtypes as follows:

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  1. 1. Epidermolysis bullosa simplex (EBS, with intraepidermal bullae)

    • Major subtypes:
      • EBS, Weber—Cockayne.
      • EBS, Koebner.
      • EBS, Dowling—Meara.
      • EBS with muscular dystrophy.
    • Minor subtypes:
      • EBS with mottled pigmentation.
      • Autosomal recessive EBS.
      • EBS, Ogna.
      • EBS with pyloric atresia.
      • EBS superficialis.

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  1. 2. Junctional epidermolysis bullosa (JEB, with lucida bullae)

    • Major subtypes:
      • JEB, Herlitz.
      • JEB, non-Herlitz.
      • JEB with pyloric atresia.
    • Minor subtypes:
      • JEB inversa.
      • JEB localized.

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  1. 3. Dystrophic epidermolysis bullosa (DEB, with subbasal lamina bullae)

    • Major subtypes:
      • Dominant (D) DEB.
      • Recessive (R) DEB, Hallopeau-Siemens.
      • RDEB, non–Hallopeau-Siemens.
    • Minor subtypes:
      • DDEB, pretibial.
      • DDEB pruriginosa.
      • RDEB inversa.
      • RDEB centripetalis.
      • DEB, transient bullous dermolysis of the newborn.
      • DEB, autosomal, dominant/autosomal, recessive heterozygote.

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Epidermolysis Bullosa Simplex

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Epidermolysis bullosa simplex (EBS) is typically an autosomal dominantly inherited, typically nonscarring, blistering disorder which leads to cleavage within the basal cell layer of the epidermis.

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There are at least four subtypes of EB simplex (excluding EBS superficialis and EBS because of plectin defects), all of which have a mutation in the genes coding for Keratin 5 or Keratin 14 which are found in the basal keratinocyte:

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  • Major subtypes:
    • EBS, Weber—Cockayne (localized EBS).
    • EBS, Koebner (generalized EBS).
    • EBS, Dowling—Meara (EBS herpetiformis).
    • EBS with muscular dystrophy (MD).

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There are more rare autosomal recessive generalized EB simplex forms with a mutation in the gene that encodes for plectin (found in the hemidemsosomes of the basal keratinocyte and in the skeletal muscle):

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  • Minor subtypes:
    • EBS with mottled pigmentation.
    • Autosomal recessive EBS.
    • EBS, Ogna.
    • EBS with pyloric atresia.
    • EBS superficialis (unknown genetic defect, intraepidermal blister just beneath the granular layer).

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Synonym Epidermolytic EB.

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Epidemiology

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Age

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  • Major subtypes:
    • EBS, Weber—Cockayne: Blisters may appear in first 2 years of life. It can also begin in adolescence.
    • EBS, Koebner: Bullae at birth, at areas of friction; improves in adolescence.
    • EBS, Dowling—Meara: Bullae at birth; widespread, severe, and extensive spontaneous blisters; improves in adolescence.
    • EBS with MD: Bullae at birth.

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Incidence 10 per 1 million live births. Weber—Cockayne variant is most common, estimated at 1/50000 live births.

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Gender M = F.

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