Author: Vanessa Ngan, Staff Writer. Updated by Chief Editor, A/Prof Amanda Oakley, January 2015.

What is ichthyosis?

Ichthyosis is a disorder of cornification, characterised by persistently dry, thickened, “fish scale” skin. There are at least 20 varieties of ichthyosis, including inherited and acquired forms.

Who gets ichthyosis?

Inherited forms of ichthyosis

Inherited forms of ichthyosis may be congenital or have delayed onset.

Ichthyosis can also be due to new spontaneous mutation.

Acquired ichthyosis

Acquired ichthyosis appears in adult life. People with ichthyosis may have systemic disease, such as:

Ichthyosis may be provoked by certain medications:

What causes ichthyosis?

The inherited forms of ichthyosis occurs as a result of genetic mutations that alter the appearance and behaviour of keratinocytes (skin cells) in the stratum corneum (the outer skin barrier layer).

The cause of acquired ichthyosis is unknown.

How are inherited ichthyoses classified?

Names and classification of ichthyoses are evolving with greater understanding of the molecular causes of the diseases (1). The mutated genes are shown in italics.

Common ichthyoses

The common ichthyoses are:

Autosomal recessive congenital ichthyosis

Keratinopathic ichthyoses

This group has keratin mutations. The main types of keratinopathic ichthyoses are:

* Previously called epidermolytic hyperkeratosis or bullous ichthyosiform erythroderma
¶ Previously called ichthyosis bullosa Siemens
§ Previously called ichthyosis hystrix

There are many other rare types of ichthyosis with defined gene abnormalities and clinical features.

What are the clinical features of ichthyosis?

Ichthyosis varies in appearance and severity depending on the cause and the effect of modifying genes.

Type of ichthyosisClinical features
Ichthyosis vulgaris
  • Skin may appear normal at birth
  • By the age of 5, skin is dry with fine white scale
  • Affects abdomen, arms and legs, sparing creases of arms and legs
  • Causes keratosis pilaris
  • Palms are excessively lined
  • Associated with atopic eczema in 50%
Recessive X-linked ichthyosis
  • Generalized fine or rhomboid grey/brown scale is present at or within 6 months of birth
  • Scaling is most prominent over the extremities, neck, trunk, and buttocks
  • Palms are normal
  • Corneal opacities in 50%
  • Only affects males
  • Undescended testicles in 5–20%
Autosomal recessive congenital ichthyosis-1 (ARCI1)
  • The baby is encased by collodion membrane at birth, which cracks and is then shed; 10% are self-healing
  • Harlequin ichthyosis: severe collodion membrane, ectropion (drooping lower eyelids), eclabium (out-turned lips) and contractures
  • Lamellar ichthyosis: plate-like dark scaling over the whole body, including creases of arms and legs
  • Bathing suit variant: localised to scalp and trunk (warmer sites of the body)
  • Nonbullous congenital ichthyosiform erythroderma (NCIE): erythroderma and fine white, superficial, semiadherent scales
  • Palmoplantar keratoderma varies with affected gene
Keratinopathic ichthyoses
  • Skin is moist, red, and tender at birth
  • Fluid filled blisters may occur which may become infected and give rise to a foul skin odour
  • Thick, generalized white to brown scaling occurs within a few weeks especially over extensor joints
  • Epidermolytic ichthyosis may cause slowly extending annular polycyclic erythematous plaques
  • Porcupine or spiky appearance in ichthyosis Curth-Macklin, due to varied thickness of scale
  • KT-1 mutation causes palmoplantar keratoderma (KRT-10 does not)
  • Growth failure may occur
  • Mosaic form causes epidermal naevus
Acquired ichthyosis
  • Resembles ichthyosis vulgaris but develops in adult life
  • May have underlying disease, most often Hodgkin lymphoma
  • May be on a drug known to cause dry skin

More images of ichthyosis ...

Ichthyosis syndromes

Ichthyosis is found in several congenital syndromes. These include:

How is ichthyosis diagnosed?

Ichthyosis is usually a clinical diagnosis. Genetic testing is available in some centres. Prenatal testing may be available for X-linked ichthyosis.

Recessive X-linked ichthyosis is confirmed by absent steroid sulphatase in fibroblasts and elevated plasma cholesterol sulfate levels.

Biopsy reveals:

What problems does ichthyosis cause?

People who have very severe ichthyosis may need to spend several hours each day caring for their skin so they can lead as much of a normal life as possible. At some point during their life people with severe ichthyosis may come against some of the following problems:

What is the treatment for ichthyosis?

There is no cure for the inherited forms of ichthyosis. The following may be useful:

What is the outlook for ichthyosis?

The most severe forms of ichthyosis may threaten the life of an affected newborn but most people with ichthyosis have normal lifespan.

The following skin care tips may help:

Inherited forms of ichthyosis persist lifelong.

Acquired ichthyosis may resolve if the underlying cause can be effectively treated or a causative drug discontinued.

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