(See also Itching Itching Itching can be very uncomfortable. It is one of the most common reasons people see doctors who specialize in skin disorders (dermatologists). Itching makes people want to scratch. Scratching... read more and Dry Skin (Xeroderma) Dry Skin (Xeroderma) Xeroderma is ordinary dry skin. (See also Itching.) Normal skin owes its soft, pliable texture to its water content. To help protect against water loss, the outer layer of skin contains oil... read more 
.)
Ichthyosis is a form of severe dry skin. Ichthyosis causes scale to form on the skin in excessive amounts. Scale is areas of heaped-up, dead skin cells that appear as flaky, dry, rough patches.
Unlike xeroderma Dry Skin (Xeroderma) Xeroderma is ordinary dry skin. (See also Itching.) Normal skin owes its soft, pliable texture to its water content. To help protect against water loss, the outer layer of skin contains oil... read more , which is ordinary dry skin, ichthyosis is dry skin that results from an inherited disorder (called inherited ichthyosis) or from a number of other disorders or drugs (called acquired ichthyosis).
Inherited ichthyoses
Inherited ichthyoses (the most common forms) are the result of genetic mutations that are usually passed on from parent to child but that sometimes occur spontaneously. Inherited ichthyoses are seen at birth or develop during infancy or childhood. There are many different types of inherited ichthyoses. Some affect only the skin, and others are just one part of inherited disorders that affect other organs.
Depending on the form, the scale may be fine or it may be large, thick, and warty. Scale may form on only the palms of the hands and soles of the feet, or it may cover most of the body. Some forms cause blisters, which may lead to bacterial infections.
Acquired ichthyoses
Acquired ichthyoses may be caused by a number of internal disorders, such as an underactive thyroid gland (hypothyroidism Hypothyroidism Hypothyroidism is underactivity of the thyroid gland that leads to inadequate production of thyroid hormones and a slowing of vital body functions. Facial expressions become dull, the voice... read more 
), lymphoma Overview of Lymphoma Lymphomas are cancers of lymphocytes, which reside in the lymphatic system and in blood-forming organs. Lymphomas are cancers of a specific type of white blood cells known as lymphocytes. These... read more 
, and AIDS Acquired immunodeficiency syndrome (AIDS) Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and is treated with antiretroviral medications. If untreated, it can cause... read more 
. Some drugs can cause acquired ichthyosis (such as nicotinic acid, triparanol, and butyrophenones). Acquired ichthyoses typically develop during adulthood.
Diagnosis of Ichthyosis
Development of characteristic scales
For inherited ichthyoses, tests and consultation with a geneticist
For acquired ichthyoses, sometimes skin biopsy
Inherited ichthyoses are diagnosed when infants are born with or children develop the characteristic scales on their skin. Doctors do tests and consult experts in genetics (geneticists) to determine the cause of inherited ichthyoses.
Acquired ichthyoses are diagnosed when people develop the characteristic scales after taking a drug or developing an internal disorder. Doctors may do a skin biopsy Biopsy Doctors can identify many skin disorders simply by looking at the skin. A full skin examination includes examination of the scalp, nails, and mucous membranes. Sometimes the doctor uses a hand-held... read more 
, which can sometimes determine an internal cause.
Treatment of Ichthyosis
Moisturizers
For acquired ichthyoses, treatment of cause
For inherited ichthyosis, vitamin A–related prescription drugs
For possible infection, antibiotics
For acquired ichthyosis, the underlying disorder is treated or the drug causing the ichthyosis is stopped. Other treatments include keeping the skin moist with moisturizers and avoiding having the skin dry out.
Moisturizers containing petroleum jelly, mineral oil, salicylic or lactic acid, ammonium lactate, ceramides, or urea should be applied immediately after bathing while the skin is still wet. Excess moisturizer can be removed by blotting with a towel.
To help remove the scales, adults can apply a solution of propylene glycol in water to the affected areas after bathing. The areas are then covered with a thin plastic film or bag overnight. The solution can be applied to children twice a day, but no film is used.
For inherited ichthyosis, creams or pills containing substances related to vitamin A, such as the retinoid tretinoin, oral isotretinoin, or oral acitretin, help the skin shed the excessive scales.
People who are at risk of bacterial infection may be given antibiotics by mouth.
