Development of infections among patients with myasthenia gravis undergoing immunotherapy

Abstract Objectives Evidence on factors contributing to the development of infections in myasthenia gravis (MG) patients on immunotherapy is scarce. Methods We studied 192 MG patients attending our hospital between April 2000 and May 2021. We examined the data of patients who had undergone immunotherapy and developed an infection and analyzed factors influencing infectious events including MG severity, antibody type, thymoma, thymectomy, treatment regimens and duration, and status of MG. Results A total of 148/192 (77%) patients (52 men, mean onset 43 y) underwent immunotherapy. Of these, 22/148 (14.8%) patients developed an infection‐related hospitalization within 10 y of starting immunotherapy. Respiratory infections occurred in 14/22 (63.6%) of patients. The infections were fatal in 6/22 (27.2%) of patients. Infection‐associated myasthenic crisis developed in 4/22 (18.1%) patients. Age at MG onset was the only variable associated with the development of infection (hazard ratio [HR]; 1.056, 95% confidence interval (95% CI): 1.0291.085, P < .001). The infection‐free rate within 10 y of starting immunotherapy by MG subtype was 83.5% (95% CI: 61.4–93.5%) in ocular‐MG ( n = 29), and 87.5% (95% CI: 72.3–94.7%) in generalized early‐onset MG ( n = 55), 46.1% (95% CI: 21.7–67.6%) in generalized late‐onset MG ( n = 22), 87.7% (95% CI; 66.3–95.9%) in thymoma‐associated MG ( n = 29). Patients with muscle‐specific tyrosine kinase antibody‐positive MG ( n = 2) and antibodies‐negative MG ( n = 11) did not experience infections. Conclusion Age at onset of MG was a significant contributor to the development of infection. Generalized late‐onset MG is the most susceptible to infection and should be carefully monitored during immunotherapy.