What Is Psoriasis?

Definition of psoriasis

Psoriasis is a chronic (lasting over the course of years) skin disease. It occurs when skin cells start reproducing much faster than normal, and pile up on the surface.

Psoriasis symptoms

The most common symptoms of psoriasis are thick, red patches known as plaques, and dry, silvery scales. These appear most often on the scalp, face, elbows, knees, palms, and soles of the feet. About half the people who live with psoriasis also see changes in their toenails or fingernails; these may include pitting, discoloration, shape changes, or even loss of the entire nail.

Nearly one quarter of the population with psoriasis also experiences arthritic symptoms in their joints. This could be a distinct condition known as psoriatic arthritis.

Causes of psoriasis

Psoriasis and your immune system are closely linked. Psoriasis occurs when your immune system (your natural protection against bacteria, viruses, and other foreign invaders) does not work properly, and starts changing the behavior of your own skin cells. No one knows what triggers this.

A small group of scientists believe that bacteria and fungi may activate psoriasis.

Heredity is likely to have some role in this condition. If you have one parent with psoriasis, you have a 25% chance of having it too. If both your parents have it, your chances are 50%; you are also more likely to develop psoriasis earlier, and with more severe symptoms.

But some people with no family history have severe psoriasis, too. For this reason, it is believed that a combination of factors may cause the disease.

Who psoriasis affects

Research indicates that between 4.5 and nearly 7 million people in the U.S. have psoriasis. It affects men and women at equal rates and affects all age groups. On average, psoriasis begins between ages 15 and 35, but it can begin at any time. About 10% to 15% of people with psoriasis develop the condition before they’re 10 years old.

Although about 80% of people with psoriasis have what is known as plaque psoriasis, there are other types of psoriasis as well.

Diagnosing psoriasis

Often, the classic symptoms of psoriasis are easily identified:

• Thick, red patches of skin, or plaques
• Dry, silvery scales of skin

But sometimes psoriasis is more difficult to identify. The diagnosis is typically made by a dermatologist, a physician who specializes in the diagnosis and treatment of conditions that affect the skin, hair, nails, and mucous membranes. When the above symptoms are not evident, the dermatologist will look for:

• A family history of psoriasis
• Signs of psoriasis on the fingernails or toenails
• A pink rash in the crease of the buttocks
• Skin patches with well-defined edges

In some hard-to-diagnose cases, the doctor may also perform a skin biopsy to confirm the diagnosis.

Back to top