Backgroundв Previous the prevalence of myotonic dystrophy was identified very rare, because of the poor diagnostics. In fact, due to getting high quality of diagnostical equipments the disease is determined very common among people in the world. According to some researchers’s statistical data during 1980-1990 years, the prevalence was 1.1 in England, 2.4 in South Ireland, 5.0 in Switzerland per 100.000 population.Goal. The study was aimed to establish the prevalence of myotonic dystrophy in MongoliaMethod. In this study which is a part of a general epidemiological study of some hereditary neurological diseases in Mongolia since 1997, authors established the prevalence of myotonic dystrophy among 1.7 million population from 14 aimags and the capital city Ulaanbaatar during the period from 1997 to 2010.Results. The prevalence by aimags was ranged from 0.0 to 27.06 per 100.000 population. The average nationwide prevalence is 5.63 per 100.000. Several aimags, especially Gobi-Altai, Orkhon and Khuvsgul are high prevalence with over 3-5 times the average. But in Dornod, Bayan-Ulgii, Dundgobi, Zavkhan, Uvurkhangai, Khentii aimags didn’t have a case of myotonic dystrophy in their population. The rest of aimags have a prevalence from 2.45 (Uvs) to 5.0 (Ulaanbaatar) per 100.000 population.Conclusion1. The relatively high prevalence of myotonic dystrophy was determined among the Mongolian population, especially in Gobi-Altai, Orkhon and Khuvsgul aimags with over 3-5 times the average. 2. The disease is spreading through reproductive way in some isolated populations. There is also a trend of increasing incidence of the disease in urban areas apparently through mechanic way rural to urban migration. 3. The study concludes that there is a need of more intensive response to fight and prevent this disease through upgrading to the modern neurological and genetic diagnostics of the disease, and their regular and sustainable application. Consequently, there is also should be need to create and improve clinical and genetic counseling for patients with this disease.

Background. The prevalence of hereditary spastic paraplegia or Shtrumpel disease is very various in studied countries of the world. It fluctuated between 0.43 (Bulgaria) and 72.4 (South African Republic) per 100’000 population.Method. In this study which is a part of a general epidemiological study of some hereditary neurological diseases in Mongolia since 1997, authors established the prevalence of myotonic dystrophy among 1.7 million population from 14 aimags and the capital city Ulaanbaatar during the period from 1997 to 2010.Goal. The study aimed to establish the prevalence of hereditary spastic paraplegia (HSP) in Mongolia.Material and Method. This study is part of a general study of the epidemiology of hereditary neurological diseases in population of 14 aimags (provinces) and the capital city Ulaanbaatar (the total population covered by the study was 1’738’000) which is being carried out since 1997. The sizes of population in aimags and the city ranged from 47,800 (Southgobi) to 605,292 (Ulaanbaatar). This study report extrapolates the prevalence nationwide. Diagnosis was established by mainly clinical characteristicsResult. Study revealed 47 patients from 15 families. The prevalence of HSP by aimags was established from 0 to 13.48 per 100’000 population (Uvs aimag). The average nationwide prevalence (1’700’000 above) was established at 2.70/100’000. There are revealed 9 cases (19.1%) in ages of 0 and 14, 6 cases (12.8%) in ages of 14-19, 27 cases (57.5%) in ages of 20- 49 and 5 cases (10.6%) in age above 50.Conclusion1. By prevalence of HSP Mongolia belongs to countries with average prevalence. But the prevalence rates differ by aimags. Patients with HSP in Ulaanbaatar (11 cases) were covered by molecule-genetic analysis by types of the disease, revealing occurrences of II and IV subtypes. 2. Of all patients, 90% are below 50 years of age pointing to the early morbidity with this disease in the context of their early mortality. The situation reveals the need of further moleculegenetic and clinical studies of the types of this disease and of improvement of clinical and genetic counseling of HSP patients.