[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Skin](https://durgical.com/en/general-pathology/areas/skin/) › Ichthyosis

# Ichthyosis

- Lesion

In ichthyosis the skin sheds poorly and builds up thick, fish-like scales. Most forms are inherited.

Updated Nov 12, 2026

## Key points

- Ichthyosis vulgaris: commonest; filaggrin (FLG) loss-of-function, autosomal semidominant; reduced or absent granular layer; strong link with atopic dermatitis.
- X-linked ichthyosis: steroid sulfatase deficiency, boys, dark scales, corneal opacities; placental sulfatase deficiency can delay labour.
- Lamellar ichthyosis: autosomal recessive, transglutaminase-1 (TGM1); collodion baby at birth, large plate-like scales.
- Epidermolytic ichthyosis: keratin 1 or 10 mutations; blistering at birth, then thick scale; clumped keratin filaments.
- Acquired ichthyosis: Hodgkin lymphoma and other cancers, HIV, malnutrition, hypothyroidism, drugs.

## 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](https://durgical.com/en/conditions/atopic-dermatitis/) | 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](https://durgical.com/en/conditions/hodgkin-lymphoma/) | 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.

## Memory aid

Filaggrin is the glue that packs keratin: lose it and scales pile up like fish skin, and the leaky barrier invites eczema.

## 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).

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## Elsewhere in DurgiPedia

- [Skin: epidermis layers, dermis, hypodermis](https://durgical.com/en/histology/skin-epidermis-layers-dermis-hypodermis/)
- [Mendelian inheritance: autosomal dominant, recessive and X-linked](https://durgical.com/en/general-pathology/mendelian-inheritance-autosomal-dominant-recessive-and-x-linked/)

## Connections

## Related 3

- [Skin pathology: terms and reaction patterns](https://durgical.com/en/general-pathology/skin-pathology-terms-and-reaction-patterns/)
- [Eczematous dermatitis](https://durgical.com/en/general-pathology/eczematous-dermatitis/)
- [Mendelian inheritance: autosomal dominant, recessive and X-linked](https://durgical.com/en/general-pathology/mendelian-inheritance-autosomal-dominant-recessive-and-x-linked/)

## Related conditions 1

- [Atopic dermatitis](https://durgical.com/en/conditions/atopic-dermatitis/)

[← All of general pathology](https://durgical.com/en/general-pathology/)

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](https://medlineplus.gov/genetics/condition/lamellar-ichthyosis/) (MedlinePlus, US National Library of Medicine, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/ichthyosis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/ichthyosis/