Congenital ichthyosis

Definition

Derived from the Greek word meaning fish disease, ichthyosis is a congenital dermatological disease that is represented by thick, scaly skin.

Description

Icthyosis is a lifelong defect in skin growth that results in drying and scaling. It can be more or less severe, sometimes accumulating thick scales and cracks that are painful and bleed.

Causes & symptoms

The skin is made up of several layers, supported underneath by a layer of fat that is thicker or thinner depending on location. The lower layers contain blood vessels, the middle layers contain actively growing cells, and the upper layer consists of dead cells that serve as a barrier to the outside world. This barrier is nearly waterproof and highly resistant to infection. Scattered throughout the middle layers are hair follicles, oil and sweat glands, and nerve endings. The upper layer is constantly flaking off and being replaced from beneath by new tissue.

The defect in skin growth and hydration called ichthyosis is inborn. At the least it is unsightly, but it can itch relentlessly, leading to such complications of scratching as lichen simplex (dermatitis characterized by raw patches of skin). Either the cracking or the scratching can introduce infection, bringing with it many discomforts and complications.

Diagnosis

A dermatologist will make the diagnosis on sight. A search for associated problems will probably lead directly to the many treatments available.

Treatment

Most treatments for ichthyosis are topical, which means they are applied directly to the skin, not taken internally. In its pure form, ichthyosis requires two forms of treatment--a reduction in the amount of scale buildup and moisturizing of the underlying skin. Several agents are available for each purpose. Reduction in the amount of scale is achieved by keratolytics. Among this class of drugs are urea, lactic acid, and salicylic acid. Petrolatum, 60% propylene glycol, and glycerin are successful moisturizing agents, as are the many commercially available products. Increased humidity of the ambient air is also helpful in preventing skin dryness.

Because the skin acts as a barrier to the outside environment, medicines have a hard time penetrating, especially through the thick skin of the palms of the hands and the soles of the feet. This resistance is diminished greatly by maceration. Soaking hands in water macerates skin so that it looks like prune skin. Occlusion with rubber gloves or plastic wrap will also macerate skin. Applying medicines and then covering the skin with an occlusive dressing will facilitate entrance of the medicine and greatly magnify its effect.

Secondary treatments are necessary to control pruritus (itching) and infection. Commercial products containing camphor, menthol, eucalyptus oil, aloe, and similar substances are very effective as antipruritics. If the skin cracks deeply enough, a pathway for infection is created. Topical antibiotics like bacitracin are effective in prevention and in the early stages of these skin infections. Cleansing with hydrogen peroxide inhibits infection as well.

Finally, there are topical and internal derivatives of vitamin A called retinoids, that improve skin growth and are used for bad cases of acne, ichthyosis, and other skin conditions.

Prognosis

This condition requires continuous care throughout a lifetime. Properly treated, it is primarily a cosmetic problem.

Key Terms

Dermatologist

A specialist in diseases of the skin.

Keratolytic

An agent that dissolves or melts the outer layer of skin.

Further Reading

For Your Information

Books

• Baden, Howard P. "Ichthyosiform Dermatoses." In Dermatology in General Medicine. Edited by Thomas B. Fitzpatrick, et al. New York: McGraw-Hill, 1993, pp. 531-544.
• Parker, Frank. "Skin Diseases of General Importance." In Cecil Textbook of Medicine. Edited by J. Claude Bennett and Fred Plum. Philadelphia: W. B. Saunders, 1996, p. 2204.

Gale Encyclopedia of Medicine. Gale Research, 1999.