Age of onset of Huntington's disease in Tasmania.

Various aspects of the age of onset of Huntington's disease (HD) were studied using extensive Tasmanian data. The mean age of onset of those born before 1930 was determined. For the total Tasmanian population of HD sufferers, this was 48.3 years. This finding has clinical implications because the most dangerous period for "at risk" individuals is frequently stated to be between 20 and 45 years. The range of age of onset for one very large Tasmanian family (the "Brothers family") is 53 years, from the second to the seventh decade. There were no juvenile-onset cases (onset before 20 years of age) in patients born in Tasmania before 1930. Three juvenile cases have occurred in those born since 1930. Support was found for the observation of paternal transmission in juvenile-onset HD. No support was found for the observation of maternal transmission in late-onset disease (50 years and beyond).