Ichthyosis

 The Ichthyoses (plural) are a family of genetic diseases characterized by dry, thickened, scaling skin. Because each form of ichthyosis is rare and there is an overlap of clinical features among disease types, the medical community disagrees about clear definitions and classifications of its many forms. Very rare forms of ichthyosis may also exist which are not fully described in the medical literature. Regardless of these difficulties, there are approximately 28 recognized forms of ichthyosis and related skin types.

Most varieties of ichthyosis are relatively rare, affecting only one person in several tens of thousands. However, Ichthyosis Vulgaris is one exception; this form is estimated to affect one in every 250 people. Ichthyosis vulgaris is also the mildest form of ichthyosis and frequently goes undiagnosed or misdiagnosed as simply “dry skin.”

Ichthyosis can be a disfiguring disease, and as such has numerous social and psychological implications. The more severe forms of ichthyosis can cause many other problems. When the skin loses moisture, it becomes dry, tight, and rigid. This rigidity makes moving uncomfortable as it can cause the skin to crack and break open. Extreme thickening on the skin on the soles of the feet makes walking difficult for many individuals, and cracking around the fingers can make even simple tasks difficult or painful. In some types of ichthyosis the skin is very fragile and will rub off with the slightest abrasion. Cracks and abrasions then leave the skin open to infections.

Severe scaling on the scalp may interfere with normal hair growth. Thick scales elsewhere can block pores, making sweating difficult and increasing the risk of overheating. Although the outer skin is thicker in ichthyosis, it is less effective in preventing water (and calorie) loss by diffusion across the surface of the skin. The rapid turnover of the outer layers of skin, in some forms of ichthyosis, also requires additional energy. Because of these greater energy needs, some children with severe ichthyosis may have trouble taking in enough calories to grow normally.

Some people with ichthyosis have trouble closing their eyes completely because the surrounding skin is so tight. This condition, called ectropion, causes the eyelids to turn outward, exposing the red inner lid and causing continuing irritation. If it is left untreated, damage to the cornea can develop, leading to impaired vision.