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Sometimes called fish scale disease or fishskin disease, ichthyosis vulgaris is an inherited skin disorder that causes dead skin cells to accumulate in thick, dry scales on the skin's surface. These scales can be present at birth, but usually first appear in early childhood. Sometimes ichthyosis vulgaris disappears entirely for most of the adult years, only to return later.

Though most cases are mild, some cases of ichthyosis vulgaris are severe. No cure has been found and treatments are directed at controlling the signs and symptoms.

Ichthyosis vulgaris is characterized by:

• Very dry, scaly skin.
• Tile-like scales that are small, polygonal in shape.
• Scales that range in color from white to dirty gray to brown. People with darker skin tend to have darker colored scales.
• Flaky scalp.
• In severe cases, deep painful cracks in the palms and soles.

The scales usually appear on the elbows and lower legs and may be especially thick and dark over the shins. Though most cases of ichthyosis are mild, some can be severe.

Symptoms usually worsen or are more pronounced in cold, dry environments and tend to improve or even resolve in warm, humid environments.

Other less common forms of ichthyosis include:

• Lamellar ichthyosis. This severe form of the disease is present at birth and lasts throughout life. Infants with lamellar ichthyosis are born encased in a filmy membrane that's shed after 10 to 14 days, revealing skin that's covered in scales. The scales can range from fine and white to thick and dark and generally occur over the entire body, although they may be larger on the legs. Lamellar ichthyosis can be extremely disfiguring and may cause great psychological suffering for children and adults with the disease.
• X-linked ichthyosis. Starting soon after birth, this type of ichthyosis occurs only in males. The noticeable, dirty-brown scales that characterize this skin disease are most pronounced on the back of the neck, arms and behind the knees. Symptoms generally don't improve with age.
• Epidermolytic hyperkeratosis. This extremely rare form of ichthyosis is usually present at birth and begins with blistering skin. In time, the skin peels away in large sheets and becomes rough or wart-looking. It's most pronounced on the knees, elbows, wrists and other flexural areas.

The skin is an endlessly renewable organ. New skin cells at the base of the epidermis push toward the surface of the skin, where they eventually shrink, flatten and die. These dead skin cells flake off every day and are continuously replaced by more cells.

Ichthyosis, however, disrupts this pattern. It occurs when the production of skin cells is too fast or the skin's natural shedding process is too slow. This causes dead skin cells to collect into thick flakes that stick to the outer surface of skin. These thick flakes can resemble fish scales.

Most often, ichthyosis is inherited in an autosomal dominant pattern, which means that a child has to inherit only one copy of the affected gene to develop the disease. Children with the inherited form of the disorder usually have normal skin at birth but develop scaling and roughness during the first few years of life. At times, ichthyosis vulgaris may disappear during the adult years, only to return later.

Ichthyosis not caused by genetics, referred to as acquired ichthyosis, is very rare. This type usually manifests in adulthood and is usually associated with other internal diseases, such as cancer, thyroid disease or chronic renal failure.

If you suspect you or your child has ichthyosis, consult your family doctor or a dermatologist. He or she can diagnose the condition by examining the characteristic scales. Also, be sure to seek medical advice if the symptoms worsen or they don't improve with self-care measures. You may need a stronger medication to manage the problem.

A doctor can often make a diagnosis by examining the skin and the characteristic scales. If there's any doubt, he or she may perform other tests, such as a skin biopsy. This may be necessary to rule out other causes of dry, scaly skin.

To diagnose ichthyosis, he or she also takes into account:

• Personal and family history of ichthyosis
• Age when ichthyosis first started
• Presence of other skin disorders

There's no known cure for ichthyosis, so the goal of treatment is to manage the condition. In addition to home care, treatment can include prescription creams and ointments that contain alpha hydroxy acids, such as lactic acid and glycolic acid. These chemicals help control the scaling and increase skin moisture.

In severe cases, the doctor may prescribe retinoids — medications derived from vitamin A. They reduce the production of skin cells. Side effects from the medication may include eye and lip inflammation, bone spurs and hair loss, as well as birth defects if taken during pregnancy.

Although self-help measures won't cure ichthyosis, they may help improve the appearance and feel of damaged skin. These measures may be beneficial:

• Take long soaking baths to soften the skin. Then use a roughly-textured sponge, such as a loofa sponge, to remove the thickened scales.
• Choose mild soaps that have added oils and fats. Avoid deodorant and antibacterial soaps, which are especially harsh on dry skin.
• After washing or bathing, gently pat or blot your skin dry with a towel so that some moisture remains on the skin.
• Apply the moisturizer or lubricating cream while your skin is still wet or moist from bathing. Choose a moisturizer that contains urea or propylene glycol — chemicals that help keep your skin moist. Petroleum jelly is another good choice. Cover the treated areas with plastic wrap to keep the petroleum jelly from staining clothes and furniture.
• Twice daily applications of an over-the-counter product that contains urea, lactic acid or a low concentration of salicylic acid may help. Mild acidic compounds help the skin shed its dead skin cells. Urea helps bind moisture to the skin.
• Use a portable home humidifier or one attached to your furnace to add moisture to the air inside your home.