The aim of this study was to describe the incidence and clinical characteristics of Mycobacterium tuberculosis infection in SLE and RA patients in Korea where the prevalence rate of active pulmonary tuberculosis in a general population is relatively higher than in Western countries.
We reviewed the medical records of 283 SLE and 284 RA patients retrospectively and then assessed the incidence, risk factors, and clinical characteristics of active tuberculous infection. We then compared the results for the two different groups.
Tuberculosis was documented in 15 SLE and 7 RA patients with an incidence rate of 7.9/1,000 patient-years and 2.3/1,000 patient-years, respectively (p = 0.003). SLE-associated tuberculosis cases included 3 of miliary tuberculosis, 7 of pulmonary tuberculosis (including 1 case of diffuse pulmonary involvement with meningitis) predominantly involving two or more lobes at the mid-/lower lungfield, and 5 extra-pulmonary forms (joint, bone, kidney, larynx, pleura). All of the RA-associated tuberculosis cases were pulmonary forms with the majority being localized to single lobe, and only one case had a past history of tuberculosis, whereas a past history of tuberculosis and a longer duration of the underlying disease were significantly correlated with the development of tuberculosis in the SLE patients. Major organ involvement, the mean daily dosage of prednisolone, and a history of over 30 mg of daily prednisolone were not related to the development of tuberculosis. However, when we took only those patients taking corticosteroid until the diagnosis of tuberculosis for analysis, SLE patients with tuberculosis showed a higher daily dosage of prednisolone than those without tuberculosis.
Taken together, the characteristics of tuberculosis in SLE patients were: (1) a higher incidence rate, (2) more frequent extra-pulmonary involvement, (3) more extensive pulmonary involvement, and (4) a higher relapse rate than in rheumatoid arthritis. Thus, the contributory role of M. tuberculosis infection in the morbidity and mortality of patients with SLE must be emphasized, especially in areas in which this bacteria is endemic.