Huntington’s disease
16 Feb 2023
Huntington’s disease (HD) is a dominantly transmitted neurodegenerative disorder with wide variation in onset age but with an average age at onset of 40 years. HD is caused by the expansion of an unstable polymorphic tri-nucleotide (CAG)n repeat in exon 1 of the HTT gene (4p16.3). Repeats of 36 or larger are associated with disease expression, whereas repeats of 26 and smaller are normal. Intermediate numbers of repeats, could be associated with reduced penetrance whereby some develop HD and others do not.