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Genodermatoses — ichthyoses and epidermolysis bullosa
Genodermatoses are inherited skin diseases: in ichthyosis a barrier defect produces scale and dryness, and in epidermolysis bullosa (EB) a defect in anchoring proteins causes blisters after mild friction; the level of the blister sets the severity.
Why it matters in the exam
The exam shows a child with fine scale on the shins sparing the folds, with an atopic background (ichthyosis vulgaris, filaggrin), a boy with large dark scales on the neck and trunk whose mother had a prolonged labour (X-linked ichthyosis, steroid sulfatase deficiency), or a newborn "collodion baby" wrapped in a shiny membrane. In EB a newborn is shown with blisters on the hands and feet after light pressure. The question tests the gene and inheritance, the level of the split, the complications — aggressive SCC in recessive dystrophic EB, oesophageal stricture and fused fingers — and the treatment: emollients, keratolytics and systemic retinoids in ichthyosis, and wound care, nutrition and topical gene therapy in dystrophic EB. Remember that X-linked ichthyosis is also linked to corneal opacities and undescended testes, and that a collodion baby needs intensive care because of fluid loss, temperature instability and infections.
Key points
- Genodermatoses are inherited skin diseases in which a structural protein defect disrupts the skin barrier or its anchoring.
- Ichthyosis vulgaris, linked to filaggrin, is the most common and is associated with atopic dermatitis.
- X-linked ichthyosis affects boys, results from steroid sulfatase deficiency and is linked to corneal opacities and undescended testes.
- In EB the level of the split sets severity: simplex within the basal layer, junctional in the basement membrane and dystrophic below it.
- Recessive dystrophic EB is caused by COL7A1 and complicated by scars, fused fingers, oesophageal stricture and aggressive SCC.
Summary table
| Disease | Gene and inheritance | Appearance | Notes |
|---|---|---|---|
| Ichthyosis vulgaris | FLG (filaggrin), semi-dominant | Fine scale on the shins, folds spared, prominent palm lines | The most common; linked to atopic dermatitis |
| X-linked ichthyosis | STS (steroid sulfatase), X-linked recessive, boys | Large dark scales on the neck, trunk and limbs | Prolonged labour in the mother, corneal opacities, undescended testes |
| Lamellar ichthyosis and collodion baby | TGM1 and others, autosomal recessive | Newborn wrapped in a shiny membrane, later large scales, ectropion | Newborn intensive care: fluids, temperature, infections |
| EB simplex | KRT5 or KRT14, usually dominant | Blisters on the hands and feet after friction, heal without scars | Split within the basal layer; eases with age |
| Junctional and dystrophic EB | Junctional: LAMB3 and others; dystrophic: COL7A1 | Widespread blisters, mucosa, scars, fused fingers | Recessive dystrophic: aggressive SCC, oesophageal stricture; topical gene therapy |
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Sources
- Revised nomenclature and classification of inherited ichthyoses (Ichthyosis Consensus Conference), 2010 — Classification
- Consensus reclassification of inherited epidermolysis bullosa, 2020 — Types and genes
- European guidelines on management of congenital ichthyosis (ERN-Skin), 2019 — Treatment
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.