Psoriasis is a common skin disease characterized by patches of thickened, red and scaly skin, usually on the torso or arms, and can be painful and disfiguring in some cases. According to the article, psoriasis affects about 1 percent to 2 percent of the population. Previous research has shown that people with psoriasis may be at an increased risk for developing lymphoma - a group of cancers affecting the lymph tissues found mainly in the lymph nodes and spleen.
Joel M. Gelfand, M.D., of the University of Pennsylvania, Philadelphia, and colleagues investigated whether the rate of lymphoma in patients with a history of psoriasis is different from the rate of lymphoma in patients without psoriasis.
The researchers studied a random sample of 10 percent of patients 65 years or older (2,718 patients with psoriasis; 105,203 without) who were registered with a general practitioner who contributed to the General Practice Research Database (GPRD) between 1988 and 1996. The GPRD was established in the United Kingdom in 1987 and is a medical record database that holds data on more than 8 million patients including information on diagnoses and medications. The median follow-up time for the patients was 46 months (the median is the middle value; half the patients follow-up times were longer than 46 months, half were shorter than 46 months).
During the study period, the authors identified 276 lymphomas. "Patients with psoriasis had an almost 3-fold increased rate of lymphoma compared with patients without psoriasis," the authors write. "Patients 65 years or older who had psoriasis developed an additional 122 lymphomas per 100,000 patients annually."
After reviewing the medical records of patients with psoriasis who had lymphoma, the researchers found that "all patients with psoriasis who developed systemic lymphoma were treated with medications consistent with psoriasis and had outcomes consistent with the diagnosis of lymphoma (e.g. referral to an oncology service)"
"Additional studies are necessary to determine if the increased rate of lymphoma is related to psoriasis severity, psoriasis treatment, or an interaction between these risk factors," conclude the authors.
(Arch Dermatol. 2003;139:1425-1429. Available post-embargo at archdermatol.com) Editor's Note: This research was funded in part through grants from the National Institutes of Health, Bethesda, Md., and through an unrestricted grant from the Herzog Foundation to the Trustees of the University of Pennsylvania.
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