What if BOTH parents have Huntington's Disease?

[mhwebb03]

I know that if one parent has HD then there is a 50% chance that their child will inherit the disease. Because let's say H represents the dominant allele (bad) for HD.. and h represents the recessive (normal).. If one parent (Hh) carries the disease, and the other (hh) doesn't have the disease, and they have a child.. Then by use of a punnett square we can determine that the probability of getting Hh offspring is 50% and the probability of getting hh offspring is 50%. (probability of getting HH is 0%)..

okay.. but WHAT IF.. TWO people who had Huntington's had kids? then you'd potentially be looking at Hh x Hh, so there would be a 50% chance of Hh in offspring, 25% HH, 25% hh. so 25% normal. I want to know about the HH. please anybody tell me about the HH. I assume that means yes, you get the disease.. But does it progress worse and cause an earlier death or what?. I'm having trouble finding information.

If you got both dominant H's, and just having one gave you an excess of CAG sequences.. Then would that mean you'd just have a lot more CAG sequences, which IS supposed to mean that the disease is more extreme and probably more immediately fatal.

 

[Monique]

Research suggests that the age of onset appears to be the same, but the rate of disease progression is faster.

"Homozygosity for CAG mutation in Huntington disease is associated with a more severe clinical course"
http://brain.oxfordjournals.org/cgi/content/full/126/4/946

 

[oswaler]

I can provide some information about the scenario where both parents have Huntington's disease. First, it is important to note that Huntington's disease is caused by a mutation in the HTT gene, which contains a repeated sequence of CAG nucleotides. This mutation is dominant, meaning that only one copy of the mutated gene is needed for the disease to develop.

In the case of two parents with Huntington's disease, there is a 25% chance of the child inheriting two copies of the mutated gene (HH), a 50% chance of inheriting one copy of the mutated gene (Hh), and a 25% chance of inheriting two copies of the normal gene (hh). As you mentioned, the offspring with HH would have a higher number of CAG repeats and would likely experience more severe symptoms and an earlier onset of the disease.

However, it is important to note that the severity and progression of Huntington's disease can vary greatly among individuals, even with the same number of CAG repeats. This is due to other genetic and environmental factors that can influence the disease. Therefore, it is not possible to predict exactly how the disease will progress in an individual with two copies of the mutated gene.

In addition, while having two copies of the mutated gene may increase the risk of developing the disease, it does not necessarily mean that the disease will be more immediately fatal. With proper management and treatment, individuals with Huntington's disease can live for many years after diagnosis.

I hope this information helps to clarify your questions about the scenario of both parents having Huntington's disease. It is a complex disease and more research is needed to fully understand its progression and potential treatments.

 

[quicknote]

I understand your concern and curiosity about the potential outcomes of having both parents with Huntington's Disease (HD). It is important to note that HD is a genetic disorder caused by a mutation in the huntingtin gene, which leads to the production of an abnormal form of the huntingtin protein. This mutation is inherited in an autosomal dominant pattern, meaning that only one copy of the mutated gene is needed to develop the disease.

In the scenario you described, if both parents have HD (Hh x Hh), there is a 25% chance of their child inheriting two copies of the mutated gene (HH). This would result in the most severe form of HD and is known as juvenile onset HD. This form of HD typically presents at a younger age and progresses more rapidly than adult onset HD, which is caused by inheriting only one copy of the mutated gene.

Having two copies of the mutated gene does not necessarily mean that a person will have more CAG repeats, as this number can vary among individuals. However, having more CAG repeats has been associated with an earlier onset and faster progression of the disease.

It is important to note that the exact effects of having two copies of the mutated gene are still being studied and are not fully understood. Each individual's experience with HD can vary, even among those with the same genetic makeup. It is also important to keep in mind that having the mutated gene does not necessarily mean that a person will develop symptoms of HD, as there are other factors that can influence the expression of the gene.

In conclusion, having both parents with HD does increase the risk of inheriting two copies of the mutated gene and developing the most severe form of the disease. However, the exact effects and progression of HD in this scenario can vary and are still being studied. It is important to continue researching and understanding this complex disease in order to develop better treatments and ultimately find a cure.