Introduction: Although today we live in a globalised world, the ties established between the Iberian Peninsula and the countries of Latin America are particularly strong, with important migratory flows. This connection may condition the development of diseases that involve a genetic influence, which may in turn be modulated by various environmental factors. The aim of this review is to determine the descriptive epidemiology of myasthenia gravis in the Iberian Peninsula and in Latin America., Development: A literature search was conducted in Medline, LILACS and Google Scholar for the different countries of interest using the terms 'prevalence', 'incidence', 'epidemiology' and 'myasthenia gravis'. The methodology and quality were reviewed, and descriptive data about the study population as well as data on prevalence were extracted., Conclusions: Many countries lack epidemiological studies on myasthenia gravis and in others the data reported focus on one referral hospital, making it difficult to compare prevalence between countries. In the Iberian Peninsula, the prevalence is consistently above 100 cases x 106 inhabitants, the highest figures being found in the area of Osona (Barcelona) and in the province of Ourense. In Latin America, much lower prevalence figures are reported, generally below 100 x 106 inhabitants. There is a predominance of females in the early-onset forms (<50 years) and a clear increase in prevalence in the elderly population, especially in the very late onset forms (>65 years), where it is more frequent in men.