The length of the trinucleotide repeat accounts for 60% of the variation of the age of symptoms onset and their rate of progress. A longer repeat results in an earlier age of onset and a faster progression of symptoms. Individuals with more than sixty repeats often develop the<unk>  before age 20, while those with fewer than 40 repeats may remain asymptomatic. The remaining variation is due to environmental factors and other genes that influence the mechanism of the<unk> . Life expectancy in<unk>  is generally around 20 years following the onset of visible symptoms. Most life-threatening complications result from muscle coordination, and to a lesser extent, behavioral changes induced by declining cognitive function. The largest risk is pneumonia, which causes death in one third of those with<unk> . As the ability to synchronize movements deteriorates, difficulty clearing the lungs, and an increased risk of aspirating food or drink both increase the risk of contracting pneumonia. The second-greatest risk is heart<unk> , which causes almost a quarter of fatalities of those with<unk> . Suicide is the third greatest cause of fatalities, with 7.3% of those with<unk>  taking their own lives and up to 27% attempting to do so. To what extent suicidal thoughts are influenced by behavioral symptoms is unclear, as they signify sufferers' desires to avoid the later stages of the<unk> . Other associated risks include choking, physical injury from falls, and malnutrition.
Huntington's disease
Wilson's disease
Stratton Parker syndrome
Paraneoplastic syndrome
Sandhoff disease
Lupus
X-linked dystonia parkinsonism
Benign hereditary chorea