Apolipoprotein E and presenilin-1 genotypes in Huntington's disease

Huntington's disease (HD) is an autosomal dominant degenerative disease of the central nervous system manifested by involuntary movements (chorea), psychiatric manifestations, and cognitive impairment with a variable age at onset. This variability is mainly attributed to genetic factors. The so-called aging genes [e.g., those for apolipoprotein E (APOE) and presenilin-1 (PS-1) have been implicated in determining the age at onset of Alzheimer's disease, a disease sharing common clinical features with HD. In 60 unrelated patients suffering from HD (mean age at onset 40.1 years, range 20-65) we determined number of CAG repeats and the distribution of the APOE alleles (ε2, ε3, ε4) and PS-1 alleles. The results showed that: (a) The age at onset was higher in the group of patients with the ε4 allele (51.6 vs. 38.0 P < 0.002). (b) The correlation between the age at onset and the number of CAG repeats was strong in patients with the ε3/ε3 genotype while it was not detected in patients with ε3/ε4 genotype. (c) No correlation was found between age at onset and PS-1 alleles. In conclusion, APOE seems to be a significant factor influencing the age at onset of Huntington's disease.