Data regarding the risk of tuberculosis (TB) in myasthenia gravis (MG) patients receiving immunosuppressive therapy is limited, and the benefit of TB preventative therapy in these patients is uncertain. We audited observational data collected at an MG clinic in South Africa over a ~ 10-year period, of cases who received immunosuppressive therapy. The total time that the cohort was at risk (patient-years) was used as the denominator to calculate TB incidence after immunosuppressive therapy initiation. Multivariate logistic regression analysis was performed to identify differences between patients who did, and those who did not, develop TB. Of 480 cases, only two received TB preventative therapy when starting immunotherapy. Seventeen of 282 (6%) patients tested, were HIV-infected. With a median follow-up of 3.6 years (interquartile range 1;7.5), 13 (3%) patients (all HIV-uninfected) developed TB (38% within 12 months of starting immunosuppressive therapy). The incidence rate of TB in the study population (≤401/100000 person-years) was not higher than that for the hospital’s catchment area during the same period (>500/100000 population). The maximum dose of prescribed prednisone was higher in patients who developed TB compared to those who did not (median: 0.6 mg/kg/day vs 0.4; 0.002); Odds ratio for TB increased 1.26-fold for every 0.1 mg/kg/day increase in maximum dose (p = 0.001). In our TB endemic setting, receiving immunosuppressive therapy was not associated with excess TB in MG patients. Preventative therapy may be considered in those who are at greatest risk of developing TB and receiving high-dose prednisone.
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