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What

X-linked ichthyosis (XLI) is an inherited skin condition characterized by dry, thick, FISH-like scaling of the skin. “Ichthy” means FISH in Greek. There are several different types of ichthyosis and XLI is the mildest of all ichthyosis conditions.

Who

XLI is estimated to occur in 1 out of 6000 boys, but exactly how often it occurs is not known. Because XL1 is an X-linked disorder most patients are boys. All races and ethnicities are affected equally.

Signs and Symptoms

Children with XLI usually have symptoms at birth or in early infancy. The baby may require delivery by cesarean-section or forceps assisted vaginal delivery because this disorder can affect the mother’s cervix, causing it to not dilate adequately. Initially, the scales on the skin are tiny and white. As the child gets older, the scales become thick, brown and plate-like. They are arranged in a pattern like the scales on FISH or lizards. They may also give the appearance of dirty skin. Scales are especially obvious on the back of the neck, under the ears, and on the chest, knees, elbows, buttocks, and scalp. The armpits, the insides of the elbows as well as the groin and neck regions may also be involved. The palms and soles are usually spared. Scaling on the head fades with time. Scaling improves in hot and humid environments and worsens during dry winter months. XLI is associated with clouding of the cornea, the clear part of the eye covering the pupil. Testicles may not be descended into the scrotum (cryptorchidism) in 20% of boys. This is a risk factor for testicular cancer.

Possible Causes

XLI is not caused by infection, so it is not contagious. It is an inherited genetic disorder and cannot be prevented. Boys inherit a gene with a change (mutation) on the X chromosome from their mother, who typically does not have symptoms. Girls are usually only affected if both X chromosomes carry a genetic change. When women are carriers of the mutated gene, there is a 50% chance that each of their sons will have XLI. All of the daughters of an affected male will be carriers, but none of the sons will be affected. In some cases, new spontaneous mutations, not inherited from a parent, may be responsible for XLI. XLI is caused by a change in a gene named STS on the X chromosome. The STS protein is involved in the breakdown of certain cholesterol molecules. When the STS gene has a genetic change, the turnover of the skin lining is reduced. This results in the scaling seen in ichthyosis.

Diagnosis

The diagnosis of XLI is suggested by the skin findings that are usually present at birth or by the first birthday. A small piece of skin can be taken by a skin biopsy and studied to help in the diagnosis of XLI, differentiating it from other causes of ichthyosis. The family history, if other affected family members are known, can also help make the diagnosis.

Treatment

There is no cure for XLI. Symptoms are usually very mild and usually do not need treatment. Good advice, however, is to keep the skin well-moisturized and to prevent infection and skin tightening. Skin moisturizers are crucial and should be applied daily after bathing while the skin is still wet. There are many medications that can help with the management of this disorder. A special class of skin care products called alpha-hydroxy acids can help decrease the thickness of the skin. Topical salicylic acid can also help remove the scaling. Topical retinoic acids can decrease scaling as well. Oral retinoids are reserved for severe cases because they can have serious side effects. Topical antibacterial ointments are useful to prevent and treat skin infections and control skin odor. If the testes have not descended by one year of age, surgery may be required. Regular examination is important to screen for testicular cancer. Also, regular follow up with an eye doctor (ophthalmologist) is important to monitor for corneal clouding, which can lead to blindness.

Prognosis

XLI generally has a very good prognosis. The skin problem is usually mild and patients have normal life spans. Cosmetic and infectious complications can be reduced by aggressive daily skin care.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

Foundation for Ichthyosis & Related Skin Types, Inc. (F.I.R.S.T.)
Provides education and support networks for families.

Ichthyosis Information
Contains children’s chat rooms and education for families.

National Registry of Ichthyosis and Related Disorders
A national registry sharing information about ongoing research projects.

Google Search for X-Linked Ichthyosis

References and Sources

Foundation for Ichthyosis & Related Skin Types, Inc. (F.I.R.S.T.). www.scalyskin.org/ Provides education and support networks for families. Ichthyosis Information www.ichthyosis.com Contains children’s chat rooms and education for families. National Registry of Ichthyosis and Related Disorders www.skinregistry.org A national registry sharing information about ongoing research projects.