Ichthyosis is a condition that causes widespread and persistent thick, dry, "fish-scale" skin.
There are at least 20 different types of ichthyosis. Some types are inherited at birth and other types are acquired during adulthood.
There's no cure for ichthyosis, but a daily skincare routine usually keeps the symptoms mild and manageable.
Most people with ichthyosis have inherited a particular faulty gene from their parent. The signs and symptoms of inherited ichthyosis appear at birth or within the first year of life.
The faulty gene affects the rate at which the skin regenerates – either the shedding of old skin cells is too slow, or the skin cells reproduce at a much faster rate than they can shed old skin. Either way, this causes a build-up of rough, scaly skin.
Ichthyosis vulgaris is the most common type of inherited ichthyosis, affecting 1 in 250 people. Signs and symptoms include:
Other inherited forms of ichthyosis are very rare and include:
Ichthyosis may develop if a baby is born with a shiny yellow membrane (collodion membrane) that sheds within the first week of life.
Once the membrane has shed, one of the following types of ichthyosis can develop:
In severe cases of congenital ichthyosiform erythroderma a child may also have drooping lower eyelids (ectropion), mild hair loss and tight skin on the fingers.
Acquired ichthyosis tends to develop in adulthood and is not inherited. It's usually associated with another condition, such as:
Certain medications can also trigger ichthyosis, including some medicines used in targeted cancer therapy, such as vemurafenib and protein kinase inhibitors.
There's no cure for ichthyosis, but moisturising and exfoliating the skin daily can help prevent dryness, scaling and the build-up of skin cells.
Your skin specialist (dermatologist) will be able to prescribe or recommend suitable moisturising treatments (emollients), which may be in the form of a cream, ointment, lotion or bath oil.
Other useful exfoliating or moisturising products include lanolin creams, products containing urea, propylene glycol, lactic acid, and other alpha hydroxy acids.
Your dermatologist may also recommend peeling creams, such as salicylic acid, to help exfoliate and moisturise your skin. However, some people may find these products irritate their skin.
Antibiotics or antiseptics may be prescribed to treat skin infections.
Steroid treatments are not effective for treating ichthyosis.
People with severe ichthyosis may need to spend several hours a day caring for their skin.
They may have the following problems:
People with severe ichthyosis may be prescribed retinoid tablets (synthetic vitamin A), which reduce the growth of overactive scaly skin. They improve the skin's appearance, but do not improve the inflammation or redness.
Vitamin D supplements may also be prescribed.
People with mild ichthyosis have a normal lifespan. However, the most severe inherited types can be life threatening.
If you have inherited ichthyosis, you'll have it for life. Acquired ichthyosis may get better if the underlying cause is identified and treated.