Objective. Chronic inflammatory conditions such as rheumatoid arthritis (RA) have been associated with malignant lymphomas. This study was undertaken to investigate which patients are at highest risk, and whether antirheumatic treatment is hazardous or protective.Methods. We performed a matched case-control study of 378 consecutive Swedish RA patients in whom malignant lymphoma occurred between 1964 and 1995 (from a population-based RA cohort of 74,651 RA patients), and 378 controls. Information on disease characteristics and treatment from onset of RA until lymphoma diagnosis was abstracted from medical records. Lymphoma specimens were reclassified and tested for Epstein-Barr virus (EBV). Relative risks (odds ratios [ORs]) for lymphomas (by subtype) associated with deciles of cumulative disease activity were assessed, as were ORs associated with drug treatments.Results. The relative risks of lymphoma were only modestly elevated up to the seventh decile of cumulative disease activity. Thereafter, the relative risk increased Conclusion. Risk of lymphoma is substantially increased in a subset of patients with RA, those with very severe disease. High inflammatory activity, rather than its treatment, is a major risk determinant.

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Objective. Because treatment with tumor necrosis factor (TNF) antagonists may increase the risk of tuberculosis (TB), and because knowledge of the risk of TB in rheumatoid arthritis (RA) not treated with biologics is scarce and of uncertain generalizability to low-risk populations, this study sought to determine the risk of TB among Swedish patients with RA.Methods. Using data from Swedish nationwide and population-based registers and data from an ongoing monitoring program of TNF antagonists, the rela- Tumor necrosis factor (TNF) plays a major role in host defense against tuberculosis (TB) (1). The frequencies of TB in phase III trials of TNF antagonists (infliximab [2] and adalimumab [3]) have suggested that treatment with TNF antagonists (infliximab in particu-