February 13, 2007

Keratosis Pilaris, Lichen Planus, Pityriasis Rosea, Psoriasis


Keratosis Pilaris

Keratosis pilaris is a common disorder in which dead cells shed from the upper layer of skin plug the openings of hair follicles.

The cause is not known, although heredity probably plays a role. Also, people with atopic dermatitis are more likely to have keratosis pilaris.

The plugs or bumps that occur in keratosis pilaris make the skin feel rough (like chicken skin) and dry. Sometimes the plugs resemble small pimples. Generally, these plugs do not itch or hurt and cause only cosmetic problems. The upper arms, thighs, and buttocks are most commonly affected. The face may break out as well, particularly in children. Plugs are more likely to develop in cold weather and to clear up in the summer.

Treatment is not needed unless the person is bothered by the appearance of the disorder. Skin moisturizers are the main treatment. Creams with salicylic acid, lactic acid, or tretinoin can also be used. Keratosis pilaris is likely to come back when treatment is stopped.

Lichen Planus
Lichen planus, a recurring itchy disease, starts as a rash of small, discrete red or purple bumps that then combine and become rough, scaly patches.

The cause of lichen planus is not known, but it may be a reaction by the immune system to a variety of drugs (especially gold, bismuth, arsenic, quinine, quinidine, and quinacrine), chemicals (especially certain chemicals used to develop color photographs), and infectious organisms. The disorder itself is not infectious.


The rash of lichen planus almost always itches, sometimes severely. The bumps are usually violet and have angular borders; when light is directed at them from the side, the bumps display a distinctive sheen. New bumps may form wherever scratching or a mild skin injury occurs. Sometimes a dark discoloration remains after the rash heals.

Usually, the rash is evenly distributed on both sides of the body—most commonly on the torso, on the inner surfaces of the wrists, on the legs, on the head of the penis, and in the vagina. About half of those who get lichen planus also develop mouth sores. The face is less often affected. On the legs, the rash may become especially large, thick, and scaly. The rash sometimes results in patchy baldness on the scalp.

Lichen planus in the mouth usually results in a bluish white patch that forms in lines. This type of mouth patch often does not hurt, and the person may not know it is there. Sometimes painful sores form in the mouth, which often interfere with eating and drinking.

Prognosis and Treatment

Lichen planus usually clears up by itself after 1 or 2 years, although it sometimes lasts longer, especially when the mouth is involved. Symptoms recur in about 20% of people. Prolonged treatment may be needed during outbreaks of the rash; between outbreaks, no treatment is needed. People with mouth sores have a slightly increased risk of oral cancer, but the rash on the skin does not turn cancerous.

Drugs or chemicals that may be causing lichen planus should be avoided, and standard treatments can be used to relieve itching. Corticosteroids may be injected into the bumps, applied to the skin, or taken by mouth, sometimes with other drugs, such as acitretin or cyclosporin. Phototherapy (exposure to ultraviolet light) combined with the use of psoralens (drugs that make the skin more sensitive to the effects of ultraviolet light) may also be helpful. This treatment is called PUVA (psoralens plus ultraviolet A). For painful mouth sores, a mouthwash containing lidocaine, an anesthetic, may be used before meals to form a pain-killing coating.

Pityriasis Rosea
Pityriasis rosea is a mild disease that causes many small patches of scaly, rose-colored, inflamed skin.

The cause of pityriasis rosea is not certain but may be an infectious agent; however, the disorder is not thought to be contagious. It can develop at any age but is most common in young adults. It usually appears during spring and autumn.


Pityriasis rosea causes a rose-red or light-tan patch of skin about 1 to 4 inches in diameter that doctors call a herald or mother patch. This round or oval area usually develops on the torso. Sometimes the patch appears without any previous symptoms, but some people have a vague feeling of illness, loss of appetite, fever, and joint pain a few days before. In 5 to 10 days, many similar but smaller patches appear on other parts of the body. These secondary patches are most common on the torso, especially along and radiating from the spine. Most people with pityriasis rosea have some itching, and in some people the itching can be severe.

Diagnosis and Treatment

A doctor usually makes the diagnosis based on the appearance of the rash, particularly the herald patch. Usually the rash goes away in 4 to 5 weeks without treatment, although sometimes it lasts for 2 months or more. Both artificial and natural sunlight may speed clearing and relieve the itching. Other standard treatments for itching may be used as needed. Corticosteroids taken by mouth are necessary only for very severe itching.


Psoriasis is a chronic, recurring disease that causes one or more raised, red patches that have silvery scales and a distinct border between the patch and normal skin.

The patches of psoriasis occur because of an abnormally high rate of growth of skin cells. The reason for the rapid cell growth is unknown, but a problem with the immune system is thought to play a role. The disorder often runs in families. Psoriasis is common, affecting 2 to 4% of whites; blacks are less likely to get the disease.


Psoriasis begins most often in people aged 10 to 40, although people in all age groups are susceptible.

It usually starts as one or more small patches on the scalp, elbows, knees, back, or buttocks. The first patches may clear up after a few months or remain, sometimes growing together to form larger patches. Some people never have more than one or two small patches, and others have patches covering large areas of the body. Thick patches or patches on the palms of the hands, soles of the feet, or skinfolds of the genitals are more likely to itch or hurt, but many times the person has no symptoms. Although the patches do not cause extreme physical discomfort, they are very obvious and often embarrassing to the person. The psychologic distress caused by psoriasis can be severe. Many people with psoriasis also have deformed, thickened, pitted nails.

Psoriasis persists throughout life but may come and go. Symptoms are often diminished during the summer when the skin is exposed to bright sunlight. Some people may go for years between occurrences. Psoriasis may flare up for no apparent reason or as a result of a variety of circumstances. Flare-ups often result from conditions that irritate the skin, such as minor injuries and severe sunburn. Sometimes flare-ups follow infections, such as colds and strep throat. Flare-ups are more common in the winter and after stressful situations. Many drugs, such as antimalarial drugs, lithium, and beta-blockers, can also cause psoriasis to flare up.

Some uncommon types of psoriasis can have more serious effects. Psoriatic arthritis produces joint pain and swelling (see Rheumatoid Arthritis and Other Types of Inflammatory Arthritis: Psoriatic Arthritis). Erythrodermic psoriasis causes all of the skin on the body to become red and scaly. This form of psoriasis is serious because, like a burn, it keeps the skin from serving as a protective barrier against injury and infection. In another uncommon form of psoriasis, pustular psoriasis, large and small pus-filled blisters (pustules) form on the palms of the hands and soles of the feet. Sometimes, these pustules are scattered on the body.


Many drugs are available to treat psoriasis. Most often, a combination of drugs is used, depending on the severity and extent of the person's symptoms.

Topical drugs (drugs applied to the skin) are used most commonly. Nearly everyone with psoriasis benefits from skin moisturizers (emollients). Other topical agents include corticosteroids, often used together with calcipotriene, a vitamin D derivative, or coal or pine tar. Tazarotene or anthralin may also be used. Very thick patches can be thinned with ointments containing salicylic acid, which make the other drugs more effective. Many of these drugs are irritating to the skin, and doctors must find which ones work best for each person.

Phototherapy (exposure to ultraviolet light) also can help clear up psoriasis for several months at a time. Phototherapy is often used in combination with various topical drugs, particularly when large areas of skin are involved. Traditionally, treatment has been with phototherapy combined with the use of psoralens (drugs that make the skin more sensitive to the effects of ultraviolet light). This treatment is called PUVA (psoralens plus ultraviolet A). Some doctors are now using narrow-band ultraviolet B (UVB) treatments, which are equally effective but avoid the need to use psoralens and the side effects they cause, such as extreme sensitivity to sunshine.

For serious forms of psoriasis and psoriatic arthritis, drugs taken by mouth are used. These drugs include cyclosporine, methotrexate, and acitretin. Cyclosporine is an immunosuppressant drug. Cyclosporine may cause high blood pressure and damage the kidneys. Methotrexate interferes with the growth and multiplication of skin cells. Doctors use methotrexate for people whose psoriasis does not respond to other forms of therapy. Liver damage and impaired immunity are possible side effects. Acitretin is similar to the acne drug isotretinoin and is particularly effective in pustular psoriasis but often raises fat (lipid) levels in the blood and might cause problems with the liver and bones. It can also cause birth defects and should not be taken by a woman who might get pregnant.

Adapted from: Merck & Co., Inc.