<prompt> Answer this question truthfullyWhat are the epidemiology and demographics of myasthenia gravis?  <response>: <reason> The incidence of Myasthenia gravis is approximately 7-23 new cases per year. The prevalence of Myasthenia gravis is approximately 70-320 per million and increasing since 20 th century. The age of onset in Myasthenia gravis follows a bimodal distribution. The early type before age of 50 is female predominant and the late type after age of 60 is male predominant. Between the age of 50-60 there is no significant different between male and female. Some studies demonstrated that the incidence, prevalence and the severity of this disease is higher in AfricanAmericans. 