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What is psoriasis?

Psoriasis is a chronic inflammatory disease that causes skin and joint symptoms and predisposes to other diseases.

Alaselkä, jossa on psoriasista.
Alaselkä, jossa on psoriasista.

About psoriasis

Psoriasis is a chronic inflammatory disease that causes skin and joint symptoms and predisposes to other diseases. Susceptibility to psoriasis is inherited.

In Finland, about 2 percent of the population, or about 100,000 people, suffer from psoriasis. Of them, 5–10 percent have severe psoriasis. Psoriasis is not contagious.

According to a statement by the WHO psoriasis is a chronic, non-contagious, painful and debilitating disease for which there is no cure.

Hereditary and external causes

The development of psoriasis is associated with hereditary predisposition, which is transmitted through several genes. Because the disease is multifactorial, it may be passed on over a few generations. Not everyone with a hereditary predisposition develops symptoms. 

According to the Current Care Guidelines for Psoriasis (in Finnish), the risk of developing the disease is 14–28% if one of the parents has psoriasis. If both parents suffer from psoriasis, the risk is 41–65%.

In addition to hereditary predisposition, many external factors contribute to the onset of psoriasis. These include infectious diseases and other infections, poor oral hygiene, skin damage, heavy alcohol consumption, smoking, obesity and stress. These factors can also worsen the symptoms of psoriasis.

Regular exercise is the only thing that has been shown to reduce the incidence of psoriasis. Triggers for the disease should also be avoided.

Psoriasis can occur at any age, even as a child. It is most commonly diagnosed between the ages of 15 and 25 and the ages of 50 and 65. Psoriasis occurring during adolescence has a partially different genetic background from psoriasis occurring later in life.

Symptoms and diagnosis of psoriasis

The clinical picture of psoriasis is individual and diverse. Not everyone will necessarily experience the same symptoms.

A person with psoriasis may have skin symptoms, joint symptoms or both. Psoriasis is also often accompanied by nail symptoms. Inflammation associated with psoriasis can cause long-term fatigue.

Psoriasis can occur anywhere on the skin. The most typical places are the elbows, knees and scalp. Skin symptoms are often clearly defined red and raised patches that can flake and itch. Rash caused by psoriasis may appear where the skin is damaged or chafed. This is called the Koebner phenomenon.

Symptoms range from a few patches to a full-body rash. The severity and symptoms of psoriasis can also vary in the same person at different times. There may be long periods when the symptoms are milder or disappear completely. The clinical picture of the disease includes seasonal changes: the symptoms are often worse in winter and milder in summer.

Symptoms of psoriatic arthritis include pain, stiffness, swelling and warmth in joints and tendons. The joints may feel sore and stiff, especially in the mornings. The fingers and toes may have sausage-like swelling, or dactylitis. In addition, the attachment points of tendons and muscle membranes can become inflamed. This is called enthesitis.

Approximately 30% of people with skin psoriasis also have psoriatic arthritis. It is common forjoint symptoms to appear years after the appearance of skin symptoms, but they can also appear before or without any skin symptoms. The severity of psoriatic arthritis is independent of skin symptoms.

Psoriatic arthritis can occur in any joint of the body. The most common places are the hands, feet, ankles, knees, and elbows. Psoriatic arthritis often affects the small joints of the fingers and toes.

Psoriasis also often affects the nails. The most common symptoms are dot-like dents, the development of blotch-like patches and thickening of the nail.

Psoriasis cannot be diagnosed with laboratory tests. X-ray, ultrasound or MRI may be used to examine psoriatic arthritis. Doctors diagnose psoriasis by examining patients’ skin and joints, as well as by studying patients’ family history and other possible triggers. A biopsy can sometimes be taken from the skin to confirm the diagnosis. The diagnosis can be made most reliably by a specialist in dermatology or rheumatic diseases.

Psoriasis increases the risk of other diseases such as cardiovascular diseases, diabetes and depression. The risk of co-morbidities is reduced when the inflammation causing psoriasis is effectively treated.