[Epidemiologic study of myotonic dystrophy on the island of Mallorca].

Myotonic dystrophy (MD) or Steinert's disease is the most frequent hereditary myopathy in the adult. The aim of this study was to determine the rate of prevalence of MD on the island of Mallorca. Patients diagnosed with MD were studied in all public and private surgeries and centres able to diagnose this disease on the island of Mallorca. Therefore, this study included the whole population of Mallorca (551,129 inhabitants). A total of 60 cases were studied representing a prevalence rate of 110 cases per one million inhabitants. The patients were further classified according to the existence of family history and were geographically located into the different towns. The prevalence rate found was much higher than that described in the literature which oscillates between 30 and 50 cases per million inhabitants. Furthermore, there was a concentration of cases in 10 of the 52 towns of the island with the presence of 2 cases in 6 being significant. The rate of prevalence of the disease in the city of Palma (295,136 inhabitants) representing more than half of the population of the island was very similar (120 per million) to that found for the population as a whole.