The onset of HD seems to be correlated to the number of CAG repeats a person has in their HD gene. Generally, the higher the number of repeats the sooner is the onset.^[1] The number of repeats may change slightly with each successive generation, so that the age of onset may vary as well. Symptoms of Huntington’s disease usually become noticeable in the mid 30s to mid 40s.

Juvenile HD has an age of onset anywhere between infancy and 20 years of age. The symptoms of juvenile HD are different from those of adult-onset HD in that they generally progress faster and are more likely to exhibit rigidity and bradykinesia (very slow movement) instead of chorea.

Mortality is due to infection (mostly pneumonia), fall-related injuries, other complications resulting from HD, or suicide (The suicide rate for HD sufferers is much greater than the national average.^[2]), rather than the disease itself. Life expectancy is generally between 10 and 25 years after the onset of obvious symptoms. Huntington’s disease is a terminal illness.