CHICAGO (AP) _ People with severe psoriasis may have a higher risk of developing lymphoma and skin cancer, a study suggests.
But researchers are unsure if the risk comes from the psoriasis itself or from the drugs often used to treat the most severe cases.
Psoriasis is a lifelong disease in which the skin turns scaly, with sensitive red patches. It can be disfiguring and even disabling.
Researchers at the University of Pennsylvania found that patients with severe psoriasis who were treated with internally taken drugs were twice as likely as a control group _ people with high blood pressure _ to develop lymphomas and non-melanoma skin cancer.
There also was a slightly higher cancer risk among people with less severe psoriasis, which often is treated with lotions.
The cancer risk for those with severe psoriasis is slightly less than that of organ-transplant patients, who often receive similar immune-system suppressing drugs, said Dr. David Margolis, one of the authors of the study in Friday's issue of the Archives of Dermatology.
He said more research is necessary to determine if cancer was caused by psoriasis or the medication, or how long a person would have to be exposed to a drug before the risk increased.
A previous study found that a widely used ultraviolet-light treatment for severe psoriasis can raise the risk of melanoma, the deadliest form of skin cancer, in people who undergo years of such therapy.
Margolis' study involved 1,101 Medicaid patients who had severe psoriasis and 16,519 who had less severe cases of the disease from 1992 to 1996.
The study was supported by a grant from Novartis Pharmaceuticals Corp.