Patients with rheumatoid arthritis (RA) are at increased risk for malignant lymphoma, which appears to be a consequence of their disease or its treatment and not because of shared risk factors, a large Swedish study showed.
During the ten years that followed a diagnosis of RA, patients had an overall hazard ratio for lymphoma of 1.75 (95% CI 1.04 to 2.96, P<0.05), according to Karin Hellgren, MD, of Karolinska University Hospital in Stockholm, and colleagues.
In addition, between years six and 10 postdiagnosis, the relative risk rose to 3.48 (95% CI 1.39 to 8.72, P<0.05), the researchers reported in the May issue of Arthritis & Rheumatism.
Various studies have demonstrated that patients with established RA have a heightened risk for lymphoma, and particularly those with the most severe arthritis.
"Several explanations for the increased occurrence of malignant lymphomas in patients with manifest RA have been proposed, including various aspects of the underlying inflammation, immunosuppressive treatment, and shared genetic or environmental risk factors," the researchers wrote.
http://www.medpagetoday.com/Rheumatology/Arthritis/19963