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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).

Insight

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

Classification

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

  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.

  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.

  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.

Epidermolysis Bullosa Simplex

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.

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:

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

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):

  • 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).

Synonym Epidermolytic EB.

Epidemiology

Age

  • 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.

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

Gender M = F.

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