Tuberculosis in myasthenia gravis.

SETTING: The relationship between myasthenia gravis (MG) and tuberculosis (TB) has not been determined.

OBJECTIVE: To evaluate the relationship between MG and TB.

DESIGN: A national survey conducted between 2000 and 2006 included 2317 patients with MG identified from the Taiwan National Health Insurance database. The incidence rate ratio of TB in these patients was compared with those in 23 170 randomly selected age-, sex- and comorbidity-matched controls without MG.

RESULTS: The risk of TB was higher in the MG cohort (adjusted hazard ratio [aHR] 1.96, 95% confidence interval [CI] 1.22-3.16, P = 0.005), mainly due to an excess risk of pulmonary TB (aHR 2.10, 95%CI 1.27-3.47, P = 0.004). Age ≥60 years (HR 4.99, 95%CI 2.06-12.10, P < 0.001) and the use of corticosteroids (HR 1.12, 95%CI 1.07-1.17, P < 0.001) were risk factors for developing TB in the MG cohort. Patients with MG who developed TB had a lower 5-year survival rate than those who did not (89.4% vs. 96.0%, P = 0.032).

CONCLUSION: The incidence of pulmonary TB is significantly higher in patients with MG. Careful screening strategies for TB should be considered among high-risk patients with MG.