What is psoriasis?

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Definition of psoriasis

What exactly is psoriasis? Let’s start with what it’s not. It’s not contagious and it’s not just a skin disease. Psoriasis is a chronic skin condition. The exact cause is unknown; however, researchers believe that psoriasis has hereditary and environmental components and is mediated by the immune system.

Normally, skin cells that are formed in the deepest layers of your skin make their way to the surface. They mature, are sloughed off the body’s surface, and replaced with new skin cells from below. This cycle takes approximately a month.

In people with psoriasis, however, once the immune system is accidentally activated, an abnormally rapid skin cell cycle occurs. This means the cells move from the deepest layers of your skin to the surface in about four days. Since the cells move to the surface so quickly, they don’ t have time to properly mature. Instead, they accumulate on the skin's surface, forming raised, red patches or “lesions.”

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Psoriasis symptoms

While plaque psoriasis is the most common type of psoriasis, the disease appears in a variety of forms that can occur on different parts of the body. Each has a unique set of symptoms.

• Plaque psoriasis (psoriasis vulgaris) appears as dry, scaly patches of skin and is the most common form of the disease
• Guttate psoriasis emerges as small dots on the skin that start out pink in color and eventually become scaly
• Inverse psoriasis appears as smooth, red lesions and is found primarily in the armpits, groin, and skin folds
• Pustular psoriasis appears as small white, fluid-filled blisters that contain white blood cells
• Palmo-plantar pustulosis is a localized type of pustular psoriasis that appears on hands and feet
• Erythrodermic psoriasis develops over large areas of the body and the skin is red with excess shedding of fine scales
• Scalp psoriasis appears on the scalp as red lesions covered with scales
• Nail psoriasis can produce nail changes such as pitting, thickening, discoloration, and loosening of the nail from the nail bed

It has also been noted that people with psoriasis often develop a type of psoriasis known as psoriatic arthritis. This distinct condition occurs in from seven to 42% of people with psoriasis. In addition to skin symptoms, you may also experience joint tenderness or swelling, although a few people have joint symptoms with no skin symptoms.

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Causes of psoriasis

Over time, our understanding of psoriasis has changed. Long considered a skin disease, increasing attention and scientific information has indicated that psoriasis has genetic and environmental components and is mediated by the immune system. Researchers believe that the disease may occur when your immune system (your natural protection against bacteria, viruses, and other foreign invaders) is accidentally activated, triggering an acceleration of the normal skin cell cycle. This in turn causes an accumulation of skin cells on the surface of the skin.

While no one knows what triggers this response, heredity plays a part in it. If you have one parent with psoriasis, you have a 25% chance of getting it too. If both your parents have it, your chances are more than 50%.

On the other hand, some people with no detectable family history have psoriasis. There are various environmental factors, such as stress, injury to the skin, etc. that can trigger psoriasis. For this reason, it is believed that both genetic and non-genetic factors may cause the disease.

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Who gets psoriasis?

If you have psoriasis, you’re not alone. Research indicates that up to 10 million people in North America have psoriasis (1-3% of the population). It affects men and women at equal rates, affects all age groups, and is most common in people of European ancestry.

Although there are many different types of psoriasis, about 90% of people with psoriasis have the more common type known as plaque psoriasis.

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Diagnosing psoriasis

The classic symptoms of psoriasis are thick, raised red patches of skin covered with a dry, silvery white build-up of scales. The patches can appear anywhere on the body. While a doctor can diagnose psoriasis, it is typically done by a dermatologist – a physician who specializes in diagnosing and treating conditions that affect the skin.

Psoriasis can have a large impact on your quality of life. Knowing how various areas of your life and daily routine have changed since you began experiencing symptoms may be helpful for your doctor to determine the severity of your psoriasis.