Michael S. Okun, MD reviewing Kay C et al. Neurology 2016 Jun 22. Delatycki MB and Bandmann O. Neurology 2016 Jun 22.

Should we check for the Huntington disease gene in older patients with chorea?

The CAG trinucleotide repeat on chromosome 4 is known to underpin the occurrence of Huntington disease (HD). To estimate the frequency and penetrance of at-risk CAG repeat alleles within a general population, rather than a disease-based population, researchers assessed CAG repeats in 7315 asymptomatic individuals from British Columbia, the United States, and Scotland. Because 36 to 39 copies of the CAG repeat are associated with older age of HD onset compared with higher copy numbers, the researchers also used their data to estimate the penetrance of 36–39 CAG repeat alleles in people aged ≥65 years in British Columbia.

In the full cohort, 18 cases of ≥36 repeat alleles were identified (1 in 400), and 15 of these were 36–39 repeat alleles — much higher than previous general population estimates. The estimated penetrance of the 36–39 CAG repeat alleles was much lower than expected among people aged ≥65.

CITATION(S):

Kay C et al. Huntington disease reduced penetrance alleles occur at high frequency in the general population. Neurology 2016 Jun 22; [e-pub].

Delatycki MB and Bandmann O.Huntington disease: More common than you think? Neurology 2016 Jun 22; [e-pub]. 

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