Rare diseases · Sign or symptom

Ichthyosis

HP:0008064

What it means

An abnormality of the skin characterized the presence of excessive amounts of dry surface scales on the skin resulting from an abnormality of keratinization.

The ichthyoses are a group of skin diseases characterized by drying and scaling of skin with the accumulation of thick scales and cracks that may be painful or bleed. The abnormality in ichthyosis lies in am imbalance in the normal lifecycle of skin in which growth is matched with dying and shedding of skin cells. In ichthyosis, skin cells reproduce at a rate faster than dead skin cells can be shed or reproduce at a normal rate with a reduction in the rate of shedding. Either abnormality leads to a build up of dry and scaly skin. Note that this term refers to the morphological abnormality of the skin and not the disorder. Ichthyosis can have a congenital onset or be acuqired, e.g., paraneoplastic ichthyosis.

Rare diseases that can present with this67

Very common80–99%

32

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions, and Orphanet separately records 3 diseases where this sign is specifically absent. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Hypertrophic ichthyosis · Ichthyosiform abnormality of the skin · Ichthyotic skin

Ichthyosis

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This page uses the Human Phenotype Ontology (2026-06-23) — Human Phenotype Ontology Consortium, hpo.jax.org. Disease associations from Orphanet (INSERM), CC BY 4.0. Content is educational and is not medical advice.