Psoriasis is an inherited disorder of the skin, which causes red, scaling bumps and patches on the skin. It is a chronic disorder, which means that the symptoms come and go throughout a person's life.

What is going on in the body?

Psoriasis is an inherited disease that causes an increase in skin cells on the outer layer of the skin. In a healthy individual, skin cells mature and shed from the surface of the body about every 28 days. People with psoriasis shed skin cells every 3 to 4 days. The excess skin cells build up and form the skin lesions of psoriasis.

What are the signs and symptoms of psoriasis?

Following are the five major types of psoriasis, each with its own characteristic skin lesions:

  • erythrodermic psoriasis, which causes reddening and swelling of large areas of skin
  • guttate psoriasis, which causes small skin lesions that look like drops of fluid
  • inverse psoriasis, which causes smooth red lesions in the folds of the skin
  • plaque psoriasis, the most common type, which causes raised red skin lesions that develop silvery-white scales
  • pustular psoriasis, which forms blisters filled with thick white material

Other symptoms of psoriasis are as follows:

  • crumbling or abnormal fingernails and toenails
  • itching
  • thickening, cracking, and blistering of the palms or soles of the feet

The severity of symptoms may range from a mild cosmetic problem to a disfiguring, disabling condition.

What are the causes and risks of psoriasis?

The exact cause of psoriasis is unknown, but it is commonly believed that the body's immune system triggers the rapid growth and shedding of skin cells. Several genes have been linked to psoriasis, which tends to run in families. However, many people with psoriasis have no family history of the disease.

Certain factors seem to trigger plaque development in people with psoriasis. Suspected triggers include the following:

  • agents that damage the skin, including chemicals, electricity, and infectious agents such as bacteria
  • alcohol
  • bodywide infections, including HIV
  • excessive scratching
  • hormonal changes
  • injuries to the skin, including sunburn
  • seasonal changes in climate
  • smoking
  • some medicines, including beta-blockers, antimalarials, and NSAIDs
  • strep throat
  • stress

A person can develop psoriasis at any age. However, it most often develops in two age ranges. The first is between 16 and 22 years of age, and the second is between 57 and 60 years of age. It affects men and women equally and is seen in all races. However, psoriasis is more common in people of Western European and Scandinavian ancestry.