Plaque Psoriasis Causes

Research indicates that the disease may result from a disorder in the immune system. The immune system makes white blood cells that protect the body from infection. In psoriasis, the T cells (a type of white blood cell) abnormally trigger inflammation in the skin. These T cells also cause skin cells to grow faster than normal and to pile up in raised patches on the outer surface of the skin.

Those with a family history of psoriasis have an increased chance of having the disease. Some people carry genes that make them more likely to develop psoriasis. When both parents have psoriasis, the child may have a 50% chance of developing psoriasis. About one third of those with psoriasis have at least one family member with the disease. 

Certain factors may trigger psoriasis, such as injury to the skin, sunlight, stress, alcohol, HIV infection, smoking, and certain drugs.