Investigators assessed the incidence of ocular myasthenia gravis (MG) and identified risk factors for transformation to generalized MG.

Study design

This population-based, retrospective cohort study used data from the Rochester Epidemiology Project to identify adults diagnosed with MG over a 27-year period. Data collected included symptom onset, diagnostic testing and conversion of ocular MG to generalized MG.

Outcomes

The mean age at diagnosis was 59 years and the median follow-up time was 91 months. There were 65 cases of MG during the study period, resulting in an annual incidence of 2.20/100,000. Thirty-three patients presented with ocular disease (annual incidence 1.13/100,000); 18 of these cases converted to generalized MG at a median of 13 months (range 2–180 months).

Patients with ocular MG who were seropositive for acetylcholine receptor antibody (AchR Ab) were more likely to convert to generalized MG at 5 years compared with seronegative patients (HR 8.2). In addition, patients with a positive single-fiber electromyography (sfEMG) at diagnosis were more likely to convert to generalized disease than those with negative sfEMG (HR 5.5).

Limitations

Overall, this is a well-executed study. As with any study using an epidemiology database, there may be some errors in identifying all patients with the disease being studied.

Clinical significance

Oculoplastic surgeons are often the first physicians to identify patients with ocular myasthenia gravis. This study highlights the high percentage of patients who develop generalized myasthenia gravis, which is a potentially fatal condition. The study confirms the importance of performing antibody testing and referring patients to a neurologist for single-fiber electromyography testing and treatment.