Antititin antibody in early‐ and late‐onset myasthenia gravis

Objectives Myasthenia gravis ( MG ) is an autoimmune disease caused by antibodies against neuromuscular junction proteins, 85% of patients have antibodies against acetylcholine receptor ( AC hR‐ MG ). Antititin antibodies are present in a subset of patients with MG . We aimed to determine the value of antititin antibodies as severity markers and thymoma predictors in early‐ and late‐onset MG . Materials & methods Two‐hundred and ninety‐five consecutive MG patients (188 F and 107 M) aged 12‐89 years (mean 50y) were included. 164 patients had early‐onset ( EOMG , ≤50 years of age), 131 had late‐onset MG ( LOMG ). Twenty‐six patients had thymoma. symptoms, severity graded with MGFA scale, thymus histology, medications, and treatment results were analyzed. Results Antititin antibodies were present in 81 (27%) of all patients: 54% of thymoma MG , 0.6% of non‐thymomatous EOMG , and 55% of LOMG , with proportion of titin‐positive patients increasing linearly from 40% in the 6th to 88% in the 9th decade of life. Titin‐positive patients had more bulbar symptoms ( P  = 0.003). Severity of MG , need for immunosuppression, myasthenic crisis risk or treatment results were not related to its presence. Antititin antibodies had 56% sensitivity, 99% specificity, 90% positive predictive value ( PPV ), and 95% negative predictive value ( NPV ) for thymoma diagnosis in EOMG , and 50% sensitivity, 75% specificity, 71% PPV and 55% NPV in LOMG . Conclusions Antititin antibodies have high PPV and NPV for thymoma in EOMG . In MG without thymoma, antititin antibodies can be considered as markers of LOMG , but not of a severe course in our MG cohort.