Titin antibodies in patients with late onset myasthenia gravis: clinical correlations.

We have tested sera from 21 thymectomized patients with onset of MG after 40 years of age and without thymoma for antibodies against titin, using ELISA with the titin peptide MGT-30. Titin is a myofibrillar protein unique to striated muscle and important for the elastic recoil of muscle cells. Titin antibodies were detected in 9 of the 21 sera. MG symptoms as assessed by a 6 point disability score (0-5) were significantly more severe in the titin antibody positive patients both at peak of illness; 3.7 vs. 3.1 (p < 0.02) and at latest follow up; 2.1 vs. 0.8 (p < 0.01). All titin antibody positive patients were on immunosuppressive drug treatment at least follow-up, whereas only 3 of 12 patients without titin antibodies used immunosuppressive drugs. The presence of circulating titin antibodies in late-onset non-thymoma MG patients indicates a more severe disease.