Guttate Psoriasis Causes

An outbreak of guttate psoriasis may be an immune reaction that is triggered by a previous streptococcal infection or some other type of infection. 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 and the production of excess skin cells.

Guttate psoriasis may be inherited. 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.

People with guttate psoriasis may have a significantly higher number of human leukocyte antigens BW17, B13, or CW6 than others. Psoriasis is the only disease associated with the human leukocyte antigen C gene expression.

Antigens are proteins on the surface of bacteria, viruses, or material foreign to the body. The body's immune system recognizes the type of antigen present and makes an antibody to destroy the bacteria, virus, or foreign material.

When the body has a streptococcal infection, it produces antibodies to streptolysin-O that is on the bacterial cell. People with an excess of human leukocyte antigen B13 may not be able to produce enough antibodies to the streptolysin-O, which may be associated with the high rate of guttate psoriasis in these individuals.

Factors that may trigger guttate psoriasis include the following: 

• Streptococcal infection: As many as 80% of people with guttate psoriasis have a streptococcal infection, usually in the form of tonsillopharyngitis, before the outbreak. Even though the connection between these infections and the outbreaks has been known for over 50 years, the exact mechanism by which the infection triggers the lesions is unknown.
• Viral infections, such as chicken pox, rubella, and roseola, may also trigger outbreaks in children.