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As an only child do I have a higher risk of HD?

June 28, 2015

Huntington's Disease Youth Organization

HDYO has more information about HD available for young people, parents and professionals on our site:


As an only child do I have a higher risk of HD?

Q. My grandfather and my father had HD; do I have more chances of developing the disease, being an only child?

Nathalila, Teen, Brazil

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A. Dear Nathalila

Many thanks for your question. Being an only child will not increase the likelihood of you developing HD.

The reason for this is that someone with HD has one copy of the huntington gene that is larger than usual (called a ‘CAG expansion’, which causes symptoms of HD), while the other copy of the gene is usually a normal size (like most genes, everyone has two copies of the huntington gene). When that individual has a child, the child could inherit either copy of the huntington gene. Therefore, a child would have a 50% (1 in 2) chance of also carrying the expanded gene that causes HD. The number of children the parent has does not affect the likelihood of which gene is passed on – each child has a separate 50% chance (so for example, if there are two children, it could be that one, both, or neither of the children inherit the expansion). You may find this HDYO article helpful, as it describes how the gene can be passed on in families in more detail.

I hope this helps answer your question. Please do not hesitate to get back in touch if you have any other questions.

Best wishes