Psoriasis is caused by a faulty immune system, often involving a type of white blood cell called a T cell. T cells should work to protect your body against infection. In people with psoriasis, however, T cells become so active that they trigger other immune responses, which lead to the overproduction of skin cells.
A predisposition to psoriasis could likely begin in your genes. Some genes may have defective DNA that may "turn on and off" signals for cell production at the wrong rate.
You probably also need to be exposed to some type of "trigger" for the disease to appear. For some people, the trigger might be illness, injury or extreme stress.
There are a number of other factors that increase a person's risk of psoriasis. Some of these include:
- Obesity: If you carry extra weight, your chance of developing inverse psoriasis increases. Plaques associated with all types of psoriasis can develop in skin folds. Talk to your doctor about weight-loss and exercise goals.
- Smoking: People with a family history of psoriasis who also smoke are more likely to develop the disease and have a more severe form of it.
- Alcohol: Heavy drinking can cause flare-ups and interfere with the effectiveness of medications.
- Stress: For some people, stressful events can worsen their psoriasis.
Risk factors associated with psoriasis
People with psoriasis are at risk for the following conditions:
Psoriatic arthritis: Up to 30% of people with psoriasis go on to develop psoriatic arthritis, which causes pain, stiffness and swelling in and around the joints. Symptoms include joint pain, back pain, morning stiffness lasting more than 30 minutes, fatigue, reduced range of motion, swollen fingers and toes, and nail changes (ridges, "pitting" or separation from the nail bed).
Depression: As many as 25% of people with psoriasis may suffer from depression.
Cardiovascular disease: People with severe psoriasis may be at greater risk for heart disease.