The study, published in the November 2003 issue of the Archives of Dermatology, found that the rate of lymphoma, a cancer of the immune system, was almost three times higher for people with psoriasis. Researchers spent over 46 months examining cases of patients who were 65 years old and older in the United Kingdom. While 2,718 patients had psoriasis, 105,203 did not. Researchers found that there were 122 more lymphomas annually per 100,000 patients among the group with psoriasis, compared with those without psoriasis. However, it’s still unclear what is causing the increase.
Dr. Joel M. Gelfand, the principle investigator and an assistant professor at the University of Pennsylvania in Pittsburgh, says larger studies need to be done in determine the reason for the increase.
"People with significant psoriasis may be at risk for immune cancers like lymphoma because they have extra immune activity, which increases the risk of their immune system going awry," Gelfand says. "Or some of the treatment that suppresses the immune system could increase risk. Or the increase could be due to a combination of these factors."
Gelfand emphasizes that the rate of lymphoma among people with psoriasis is still low, but that the risks and benefits of treatments for psoriasis should be weighed carefully.