Relationship Between Age, Gender, and Race in Patients Presenting With Myasthenia Gravis With Only Ocular Manifestations.

BACKGROUND

The demographic associations among patients presenting with myasthenia gravis with only ocular manifestations (OMG) is not clear.

METHODS

In this 5-center case series, we collected the race, gender, and age at diagnosis of patients diagnosed with myasthenia gravis who had no signs or symptoms of generalized myasthenia gravis (GMG). An a priori sample size calculation determined that 140 patients were required to accept that there was a ≤10-year difference in mean age (equivalence testing: power 90%, α = 0.05). Robust Bayesian analysis and linear regression were applied to evaluate whether age differed by gender or race.

RESULTS

Of 433 patients included, 258 (60%) were men. Mean age among men was 57 years (SD = 19) and 52 years (SD = 21) among women. The 95% credible interval (CI) (Bayesian equivalent of confidence interval) was 0.8-8.7 years for mean age, and there was a 99.6% probability that the mean difference in age between sexes was <10 years. Race was documented in 376 (68 [18%] non-Caucasian). Caucasians were 17.3 years older than non-Caucasians at diagnosis (95% CI, 12.2-22.3 y; P < 0.001) controlling for gender. There was no additive interaction of gender and race (P = 0.74). There was a bimodal distribution for women peaking around 30 and 60 years. Men had a left skewed unimodal age distribution peaking at age 70.

CONCLUSIONS

The distribution of age at presentation in patients with OMG is different between men and women, similar to GMG. Non-Caucasian patients tend to develop OMG at a younger age.