High anti‐EBNA‐1 IgG levels are associated with early‐onset myasthenia gravis

Background: Myasthenia gravis (MG) is an autoimmune disorder mediated by antibodies against the acethylcholine receptor (AchR) of the neuromuscular junction in the majority of patients. Methods: Here, we examined IgG antibodies against the type 1 nuclear antigen of Epstein‐Barr virus (EBNA‐1) in the sera of 158 patients with MG compared to 184 healthy controls. Results: Although serum concentration in the sera was not different, high anti‐EBNA‐1 IgG titers (above 90th percentile of the normal values) were more common in the patients (26.6 vs. 16.3%, P = 0.024). In addition, high EBNA‐1 IgG levels occurred more frequently amongst the 94 patients with early‐onset myasthenia gravis (EOMG, 30.8%) as compared to the 64 patients with late‐onset disease (LOMG, 14.1%) ( P = 0.021). Using multiple logistic regression, high serum concentration of the anti‐EBNA‐1 IgG antibodies was significantly associated with EOMG (OR: 3.17, P = 0.027), even after adjustment for sex, presence/absence of anti‐AchR antibodies and presence/absence of anti‐Titin antibodies. Out of 39 patients with EOMG, who underwent thymectomy, 18 patients (46%) had thymoma, 6 had thymic hyperplasia (15%), and 15 patients had thymic atrophy (39%); there was no difference comparing EBNA‐1 antibody titers in the sera. As no correlation was found between the titers of anti‐AchR, anti‐Titin, and EBNA‐1 antibodies, a dysregulated heterogeneous B‐cell response was unlikely to be responsible for the elevated levels of EBV‐associated antibody in patients. Conclusions: In summary, our data suggest that high levels of EBNA‐1 antibodies are more common in MG compared to healthy controls and are especially associated with EOMG.