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What Are The Early Signs And Symptoms Of Alzheimer's Disease?
Question: Hi, I am a 51 year old female. My father developed early onset Alzheimers disease, with symptoms beginning when he was about 57 years old. Is it true that his disease is most likely familial? And, is it also true that I have a 50% chance of inheriting this trait? What kind of genetic testing is available for me?
Brief Answer:
Read below
Detailed Answer:
I read your question carefully and I understand your concern.
It is true that early onset Alzheimer's disease is the one which is mostly associated with familial cases. The earlier the onset the likelier that is, especially if under the age of 50. However to define a case as familial there is not enough to have only one family member, there can be isolated cases with early onset, usually it is defined as 3 members from 2 generations. So if the it is only the case of your father before speaking of the chance of you inheriting it one should consider it may be not such a case at all.
In those identified familial mutations it is a case of autosomal dominant transmission, meaning if you have the faulty gene you develop the disease. SO since we have two copies of each gene, your father as well, there is indeed a 50% chance of inheriting that gene (again if your father was such a case, as I said with only one member it doesn't have to be familial).
Currently there are three types of mutations known to cause familial early onset Alzheimer's, APP (amyloid precussor protein), PS1 and PS2 (presenilin 1 and 2). Genetic testing is not that widely available though, PS1 is the most commonly done while the other two are done only in big research centers. While finding such a mutation would mean you are likely to develop the disease, not having it doesn't exclude it as these are the known mutations, but there are familial forms for which the responsible gene simply hasn't been identified.
There is another gene called APOE, but it's more related to late onset disease and also it indicates simply an increased risk, having the particular form related to Alzheimer's doesn't mean that you'll develop it, so its testing value is debatable.
I hope to have been of help.
Read below
Detailed Answer:
I read your question carefully and I understand your concern.
It is true that early onset Alzheimer's disease is the one which is mostly associated with familial cases. The earlier the onset the likelier that is, especially if under the age of 50. However to define a case as familial there is not enough to have only one family member, there can be isolated cases with early onset, usually it is defined as 3 members from 2 generations. So if the it is only the case of your father before speaking of the chance of you inheriting it one should consider it may be not such a case at all.
In those identified familial mutations it is a case of autosomal dominant transmission, meaning if you have the faulty gene you develop the disease. SO since we have two copies of each gene, your father as well, there is indeed a 50% chance of inheriting that gene (again if your father was such a case, as I said with only one member it doesn't have to be familial).
Currently there are three types of mutations known to cause familial early onset Alzheimer's, APP (amyloid precussor protein), PS1 and PS2 (presenilin 1 and 2). Genetic testing is not that widely available though, PS1 is the most commonly done while the other two are done only in big research centers. While finding such a mutation would mean you are likely to develop the disease, not having it doesn't exclude it as these are the known mutations, but there are familial forms for which the responsible gene simply hasn't been identified.
There is another gene called APOE, but it's more related to late onset disease and also it indicates simply an increased risk, having the particular form related to Alzheimer's doesn't mean that you'll develop it, so its testing value is debatable.
I hope to have been of help.
Above answer was peer-reviewed by :
Dr. Chakravarthy Mazumdar
Answered by
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