From the dermatologist to the oncologist?

Psoriasis patients might be at a higher risk for lymphoma -- but it's not clear if it's the drugs or the disease

By Christopher J Lipowski

As it turns out, psoriasis, a chronic skin disease characterized by scaling and inflammation that affects nearly 3% of the Canadian population, may be more than just a skin disorder. Researchers have known for some time that psoriasis stems from problems with the immune system.

The current treatment of choice uses immunosuppressive agents such as cyclosporine and corticosteroid creams. It now appears that psoriasis may be linked to cancer of the immune system.

In a large study published in the November issue of the Archives of Dermatology, Dr Joel M Gelfand and colleagues at the University of Pennsylvania carried out a cohort study to determine the rate of lymphoma in patients with psoriasis compared to those without the skin disease. The population studied was a 10% sample of patients over 65 years of age taken from the United Kingdom General Practice Research Database. In all, 2,718 psoriasis patients and 105,203 patients without psoriasis were identified. The database sample was followed for a median time of 46 months. The investigators identified 276 lymphomas during the study period and found that those with psoriasis were 2.95 times as likely to have lymphoma compared with those without psoriasis.

Although the rate was low, the study results were cause for concern. Moreover, according to the researchers, it wasn't clear what caused the increased rate. What is certain is that more work is required to determine whether developing psoriasis is in itself enough to increase the risk of lymphoma, or whether it is only linked to severe forms of the disease.

The risk comes from the treatments used for psoriasis. In the meantime, the risks and benefits of treatments for psoriasis, especially the drugs, which suppress the immune system, should be weighed carefully and clinicians should be vigilant for symptoms of lymphoma in psoriasis patients.