The epidemiology of Huntington's disease

Abstract

The available information on the world distribution of Huntington's disease (HD) from population surveys and death rate analysis is summarised and discussed in the light of genetic studies. It is concluded that most European populations, both Northern and Southern, show a relatively high prevalence (4-8 per 100,000), and that the disorder may also be frequent in India and parts of central Asia. HD is notably rare in Finland and in Japan, but data for Eastern Asia and Africa are inadequate. The disorder may have been underestimated in the American black population. Populations derived from recent European immigration show frequencies and origins of HD comparable to those expected from their own origins and expansion; there is no evidence to suggest that the HD gene has spread disproportionally and its selective effect may be close to neutral. Multiple separate introductions of the gene have been the rule in large populations. Several major foci of HD exist as the result of rapid population expansion. It is likely that a number of separate mutations for HD will be shown to be responsible for the disease, but that the high frequency of HD in European populations will prove to be the result of one or a very small number of mutations, probably of great antiquity.

Treatment of Huntington's Disease

“…Most European populations show a prevalence rate of 4-8 cases per 100,000 [31][32][33]. HD is notably rare in Finland and Japan, but data for Eastern Asia, Africa and Black Americans are inadequate [34].…”

“…There are well-known large populations of patients with HD in Scotland and the Lake Maracaibo region of Venezuela [35,36]. There have been no widespread epidemiologic studies of HD in the USA since genetic testing became widely available in 1993, but it is estimated that approximately 25,000-30,000 individuals have manifest HD and a further 150,000-250,000 individuals are at risk for HD [37].…”

Huntington disease in the South African population occurs on diverse and ethnically distinct genetic haplotypes

“…The prevalence of HD varies geographically with the highest rates reported in European populations at approximately 5-7 affected individuals per 100 000 and significantly lower rates in Asian and African populations. 1,2 The average CAG-tract size in unaffected individuals varies between 17-20 CAG repeats across populations, whereas a CAG tract of 36 or more repeats is within the affected range. 1,3 Despite extensive characterisation of the main genetic defect underlying HD, which is identical across populations, differences in worldwide prevalence are not fully understood.…”

HTT haplotypes contribute to differences in Huntington disease prevalence between Europe and East Asia

“…1 Although HD is found worldwide, there are significant geographic differences in its prevalence. [2][3][4][5] The highest prevalence rates are reported for Western populations from Europe, where the minimum prevalence is 45 per 1 00 000 ( Figure 1 and Supplementary Table 1). The origins of HD chromosomes in the United States, Canada, South Africa, Australia, the Caribbean, the Indian Subcontinent and Venezuela can be genealogically traced to European origins 6 and have similar HD prevalence rates to Europe.…”