Q: My mother is suffering from Familial Alzheimer's disease since the age of 48 years. Is it possible that my siblings or I have received the mutated gene from my mother? Is this preventable?

A:Familial Alzheimer's disease (FAD) is an uncommon condition accounting for 5-10% of Alzheimer's cases. It starts under the age of 65 years. Three causative genes for Alzheimer's disease have been identified to date: the APP gene on chromosome 21, the Presenilin-1 (PSEN1) gene on chromosome 14 and the Presenilin-2 (PSEN2) gene on chromosome 1. The mutation (genetic fault) runs in families and is handed on from parent to child. The risk of a parent with the gene passing the mutation on to a child is 50% (autosomal dominant inheritance). If the child inherits the mutation then he/she will develop the disease, and is in turn at risk of passing the gene to their children. If they do not inherit the gene they will not develop familial Alzheimer's disease and cannot pass it on to their children, i.e. the disease does not skip generations. Testing for these mutations is possible in many large academic institutions undertaking research in Alzheimer's disease. In contrast, persons who inherit an Apolipoprotein E (E4) gene from a mother or father have a more than three-fold risk of developing Alzheimer's disease late in life, after the age of 65 years. People who inherit an E4 gene from both mother and father, have ten times the normal risk of developing Alzheimer's disease after age 65. It is not clear why or how E4 increases risk. The E4 allele is not dominant. This means that not everyone with an E4 allele develops Alzheimer's disease. Therefore, the genetic counsellors do not advise for E4 testing as it is not certain that everyone with Alzheimer's disease will have E 4 positivity and vice versa. Genetic testing of FAD, therefore, needs to be considered based on the above facts. As of now, no definite curative treatment exists for Alzheimer's disease. There are a number of general measures, which can be taken to prevent the disease, but no definite treatment is available to reverse the genetic trait or the disease. Hence, these raise a lot of ethical issues regarding the genetic testing for Alzheimer's disease including FAD. General measures that have shown to be of help in preventing Alzheimer's disease include: