Genetic aspects of psoriasis
Psoriasis is believed to be a genetic disease, but it does not follow a typical dominant or recessive pattern of inheritance. No one can predict who will get psoriasis. Researchers do not completely understand how psoriasis is passed from one generation to another. The pattern of inheritance probably involves multiple genes or combinations of many genes, and the search is on to find those genes.
There is clearly a familial component: About one out of three people with psoriasis report that a relative had psoriasis. If one parent has psoriasis, a child has about a 10 percent chance of having psoriasis. If both parents have psoriasis, a child has approximately a 50 percent chance.
Studies of genetically identical twins with psoriasis have shown that psoriasis is at least partially genetic. But those same studies also reinforce the complexity of psoriasis. In about one-third of identical twin pairs where psoriasis is present, only one twin has the disease, indicating that environmental factors probably play a role in who develops psoriasis. The theory that psoriasis is triggered by a combination of genes and external forces is called "multifactorial inheritance." Once the genes responsible for psoriasis are discovered, the inheritance pattern may be better understood.
Updated June 2006
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