Clinical characteristics of Mycobacterium tuberculosis infection among rheumatoid arthritis patients

To evaluate the clinical characteristics of Mycobacterium tuberculosis infection in rheumatoid arthritis (RA) patients, we examined the clinical manifestations and radiography/computed tomography (CT) findings in RA patients with tuberculosis (RA+/TB+). A total of 1121 tuberculosis patients were admitted to our hospital from 1995 to 2003, with the RA patients among them comprising 1.8% (20 cases; 9 men and 11 women). This is approximately three times as high as the prevalence of RA in the entire population in Japan. In addition, the RA+/TB+ patients were older and had a longer history of RA than the 140 outpatients in our RA clinic who did not have tuberculosis (RA+/TB-). Half of the RA+/TB+ patients had no symptoms (e.g., cough, sputum, pyrexia), and their tuberculosis was detected accidentally by radiography/CT. The positive rates of the bacilli in the smear and culture of the sputum from the RA+/TB+ patients were lower than those from 143 patients randomly selected from among 1091 tuberculosis patients without any collagen disease including RA (RA-/TB+). The RA+/TB+ patients had a higher incidence of extrapulmonary tuberculosis (30%), including four cases (20%) of miliary tuberculosis, an incidence seven times higher than among the general population of tuberculosis patients. Among 14 cases of pulmonary tuberculosis patients with RA, bilateral lesions and non-cavitary lesions were found in 71.4% and 64.3%, respectively, which tended to be a higher incidence than in the RA-/TB+ patients. The mortality rate and sputum conversion time of the RA+/TB+ patients were no different from those of the RA-/TB+ patients. The prevalence of tuberculosis in RA patients is expected to increase after introduction of anti-cytokine therapy in Japan, and careful observation should be done to avoid this complication in RA patients.