Late-onset Huntington’s disease associated with CAG repeat lengths of 30 and 31

Huntington’s disease across the lifespan.

“…Late-onset HD has variably been defined as diagnosis after the age of 50 or 60 (Capiluppi et al, 2020;Lipe & Bird, 2009;Sipilä et al, 2017;Stoker et al, 2021;Teodorczuk, 2007;Volpi et al, 2021;Zinzi et al, 2021). Formal consensus criteria for late-onset HD do not yet exist, and the research literature noting late-onset HD has incorporated varied participant samples.…”

“…For example, in the studies reviewed by Chaganti and colleagues (2017), the expanded allele ranged from 38 to 46 CAG repeats, with averages at about 39 to 40. Furthermore, several reports show HD arising in people with very low CAG expansion numbers, as low as 29 to 31 repeats (Garcia-Ruiz et al, 2016;Stoker et al, 2021), which is the intermediate allele range. How the phenotype occurring in this low CAG range may differ from the more common allele expansions is not known because few cases of HD arising in people with intermediate alleles have been described.…”

“…The effect on the carrier of having an allele with 27 to 35 CAG repeats is not well characterized. Controversial evidence suggests, however, that HD may (very rarely) develop, even in a person whose larger allele only contains 30 or 31 repeats (Stoker et al, 2021).…”