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Huntington's Disease Youth Organization

What do the researchers know exactly about CAG 36?

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Q. I’m really interested in scientific data about inheriting Huntington’s disease from mother who has 36 CAG repeats (father without the mutation).

What do the researchers know exactly about CAG 36? It’s the grey zone so to get ill from Huntington’s disease you must have CAG 40. Please give me as many information as possible because I’m gonna get crazy waiting 10 years until my grandson will take the DNA test. Greetings!

Ewa, Young Adult, Denmark

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A. Hi Ewa

Thanks for your question about the ‘grey area’ in Huntington’s disease. A CAG repeat size of 36 falls in to a range known as ‘reduced penetrance’ i.e. between 36-40 CAG repeats. Individuals who have an HD gene in the reduced penetrance range may never develop symptoms of HD or a proportion may develop symptoms later in life. It is encouraging that 36 CAG repeats is at the start of the reduced penetrance range. Where an HD gene in the reduced penetrance range is passed on from a mother, it is unlikely to increase in size in the next generation. If you let me know where you live in Poland, I would be happy to put you in contact with a genetics doctor to explain this more fully to you in your own language.

The predictive testing for HD website here has a full explanation of CAG repeat size and you can click to have it translated in to Polish.

Here is an article of HDBuzz that explains what we know so far about the ‘grey area’.

All the best


Last updated: March 04, 2017 08:14