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Home Books McGraw-Hill Education Specialty Board Review Dermatology: A Pictorial Review, 3e

Chapter 14: Genodermatosis

Nnenna G. Agim; Joy H. Kunishige; Marzieh Thurber; Adrienne M. Feasel; Adelaide A. Hebert

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EPIDERMOLYSIS BULLOSA (EB)

  • Disorder with the formation of bullae and erosions following mechanical trauma to the skin and mucosa

  • All types of EB patients exhibit fragile skin and blisters. Scarring, nail dystrophy, milia, and scarring alopecia occur in the forms involving the lamina lucida and below

  • Gene defects cause abnormalities in structural proteins of the epidermis and the epidermal-dermal junction

  • Subtypes are classified based on the ultrastructural level of blisters (Table 14-1), mode of inheritance, and the clinical features

  • There are four major EB types (Table 14-2) and multiple related subtypes (Table 14-3)

Table 14-1Ultrastructural Findings Among Major Types and Selected Subtypes of EB
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Table 14-1 Ultrastructural Findings Among Major Types and Selected Subtypes of EB

EB Type or Subtype

Ultrastructural Site of Skin Findings

Other Ultrastructural Findings

EB simplex (EBS)

EBS, localized

Basal layer

Split may spread to suprabasilar layer

EBS, DM

Basal layer in subnuclear cytoplasm

Dense, circumscribed clumps of keratin filaments (most commonly observed

EBS-MD

Predominantly in basal layer, above level of HD attachment plaque

Reduced integration of keratin filaments with HD

EBS-AR

Basal keratinocytes

Absent or reduced keratin filaments within basal keratinocytes

EBSS

Split usually at interface between granular and cornified cell layers

—

EBS, lethal acantholytic

Suprabasal cleavage and acantholysis

Perinuclear retraction of keratin filaments

EBS, plakophilin-1 deficiency

Midepidermal cell-cell separation

Diminutive suprabasal desmosomes; perinuclear retraction of keratin filaments

EBS-PA

Lower basal layer, above level of HD plaque

Reduced integration of keratin filaments with HD

Junctional EB (JEB)

JEB-H

Lamina lucida

Markedly reduced or absent HD; absent SBDP

JEB-nH

Lamina lucida

HDs may be normal or reduced in size and number

JEB-PA

Lamina lucida

Small HD plaques often with attenuated SBDP

Dominant dystrophic EB (DDEB)

DDEB, generalized

Sublamina densa

Normal or decreased numbers of AFs

DDEB-BDN

Sublamina densa

Electron-dense stellate bodies within basal layer; reduced AFs

Recessive dystrophic EB (RDEB)

RDEB, severe generalized

Sublamina densa

Absent or rudimentary AFs

RDEB, generalized other

Sublamina densa

Reduced or rudimentary-appearing AFs

RDEB-BDN

Sublamina densa

Electron-dense stellate bodies within basal layer; reduced AFs

AF, anchoring fibril; AR, autosomal recessive; BDN, bullous dermolysis of the newborn; DM, Dowling-Meara; EBSS, EBS superficialis; H, Herlitz; HD, hemidesmosome; MD, muscular dystrophy; nH, non-Herlitz; PA, pyloric atresia; SBDP, sub-basal dense plate.

Reprinted with permission from Fine JD, Eady RA, Bauer EA, et al. The classification of inherited epidermolysis bullosa (EB): Report of the Third International Consensus Meeting on Diagnosis and Classification of EB. J Am Acad Dermatol 2008 Jun;58(6):931–950. Epub 2008 Apr 18.

Table 14-2The Four Major EB Types
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Table 14-2 The Four Major EB Types

Level of Skin Cleavage

Major EB Type

Known Targeted Protein(s)

Intraepidermal (“epidermolytic”)

EBS

Keratins 5 and 14; plectin; α6β4 integrin; plakophilin-1; desmoplakin

Intralamina lucida ...

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