Ichthyosis
- Lesion
In ichthyosis the skin sheds poorly and builds up thick, fish-like scales. Most forms are inherited.
What it is
Ichthyoses are disorders of keratinisation in which the stratum corneum accumulates because scales are made too fast or shed too slowly. Most are inherited and appear at birth or in childhood; acquired ichthyosis in adults can signal lymphoma or other systemic disease. The type depends on the defective protein: filaggrin, steroid sulfatase, transglutaminase, or keratins.
Structure
- Compact hyperkeratosis (laminated) with a thin or absent granular layer in ichthyosis vulgaris.
- Normal or thick granular layer in X-linked ichthyosis.
- Epidermolytic ichthyosis: vacuolated upper keratinocytes with coarse keratohyalin granules (epidermolytic hyperkeratosis).
Main ichthyoses
| Type | Defect | Inheritance | Clue |
|---|---|---|---|
| Ichthyosis vulgaris | Filaggrin | Semidominant | Atopy; absent granular layer |
| X-linked | Steroid sulfatase | X-linked recessive | Boys, dark scales, corneal opacities |
| Lamellar | Transglutaminase-1 | Autosomal recessive | Collodion baby, plate scales |
| Epidermolytic | Keratin 1 or 10 | Autosomal dominant | Blisters at birth |
| Acquired | Systemic disease | None | Lymphoma, HIV, malnutrition |
Clinical notes
- Collodion babies risk dehydration, hypothermia and infection.
- New ichthyosis in an adult prompts a search for underlying lymphoma.
Test yourself
Think of the answer, then tap the question to see it.
Which protein is defective in ichthyosis vulgaris?
Filaggrin.
Which enzyme is deficient in X-linked ichthyosis?
Steroid sulfatase.
Which systemic disease classically causes acquired ichthyosis?
Hodgkin lymphoma (and other lymphomas).
Elsewhere in DurgiPedia
- Skin: epidermis layers, dermis, hypodermis
- Mendelian inheritance: autosomal dominant, recessive and X-linked
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Lamellar ichthyosis (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.