Huntington’s Disease is a debilitating fatal autosomal dominant disease that has its onset in mid-life after childbearing is usually complete. Thus, some people do not want to know if they carry the gene because they then know their medical fate. The Genetics & IVF Institute developed a non-disclosing PGD method to prevent these couples from having affected children but without informing the parents whether they have the gene.
The Dutch government decided that they will not allow this technique to prevent the unnecessary use of IVF. Couples can only prevent their children from having the fatal genetic disease if the parents are willing to do the testing and find out if they have the gene which would then mean that they need the IVF with PGD.
This article discusses the ethics issues surrounding the use non-disclosing PGD and the decision not to allow its use. See the abstract here
An autosomal dominant gene is one in which if you have even 1 copy then you have the disease. There are variants of dominance but for this discussion, we will assume that if you have the gene then you have the disease. Children of a person with Huntington’s have a 50% chance of receiving the gene. If the person tests for the gene and finds that they have it then they know that will die early of a very debilitating neuromuscular disease, sometimes called Woody Guthrie’s disease. One can easily imagine why someone would not want to know that they have the gene.
Non-disclosing PGD for Huntington’s Disease works as follows.
- The first goal is to transfer only normal embryos which do not carry the Huntington’s Disease gene
- The second goal is to prevent the parents from discovering if they carry the gene
- If the parents know the genetic results of any of the embryos then they will know if they carry the gene
- If we tell only the people who do not carry the gene that all the embryos are normal then the couples who do not get told the results know that they carry the gene
- So, we cannot tell anyone, those who carry the gene or those who do not carry the gene, what the genetic results were from the biopsy
- To prevent anyone from accidentally saying or behaving in a disclosing manner – the genetic results should be know to a single embryologist and the results are sealed
- Even if the patient believes that they have the gene, the knowledge could profoundly affect the person future behavior, so all these steps are to prevent even the guessing
- The couple prepare for the single gene PGD just as anyone would. The genetics team obtains blood samples to develop and/or test the probes
- The couple undergoes IVF with retrieval of eggs
- Ideally, the IVF team does not tell the couple the results of the egg retrieval; i.e., how many eggs were retrieved
- The embryology team does not tell the IVF team any of the embryology details such as fertilization or number of embryos etc.
- Almost any information might be used to indicate the likelihood of the patient having the gene
- The woman then undergoes either a real embryo transfer or a sham transfer, with the purpose of disguising the presence or absence of embryos and a tendency to “game the system”
- If there are normal embryos in excess then hey can be frozen and the patient will be told. Since many patients do not get freezing, the absence of freezing is not any indication of the genetic results