I found out that I am a carrier for this rare disease that is similar to Tay-Sachs, but I was curious if anyone knows the actual odds of being a carrier? I know the odds of a child being born with Sandhoff if both parents are carriers, what I was wondering is if anyone knew the odds of being a carrier? Sandhoff disease can occur in any ethnic group, though it is uncommon. Individuals NOT of Jewish ancestry are more likely to carry one of the gene mutations that causes Sandhoff disease than those of Jewish ancestry (1 in 600 vs. 1 in 1,000 chance of carrying a mutation in this gene)--roughly, a .2% chance.
There is a 50 percent (2-in-4) chance that the child will inherit one normal and one abnormal gene. The child will not have the disease but will be a carrier like the parents.
If only one parent is a carrier, none of that person鈥檚 children can inherit the disease. However, each child has a 50 percent chance of inheriting the gene mutation and being a carrier.
You have a 25 percent (1-in-4) chance of having a child with Sandhoff disease if BOTH you and your spouse are carriers.
Since Sandhoff is a recessive genetic disorder, both parents must be carriers for Sandhoff disease in order to have a child with Sandhoff disease. Genes come in pairs, and a carrier of Sandhoff disease has one 脽 subunit for Hex-A and Hex-B that works and one that does not. This means carriers have about half the normal amount of Hex-A and Hex-B activity, but that鈥檚 still enough for them to be completely healthy. However, if each parent passes the non-working copy of the 脽 subunit gene to his/her child, the child will develop Sandhoff disease. Statistically speaking, if both parents are carriers, they have a 25 percent chance of having a child with Sandhoff disease with each pregnancy.
Because of the nearly total absence of hexosaminidase activity in affected individuals, laboratory diagnosis of an affected child as well as prenatal diagnosis is accurate and reliable. However, enzyme assay for the adult carrier requires special care and careful standardization of the laboratory test. DNA analysis are also available for families in which the specific beta-subunit mutations have been identified; when these are known, the DNA-based tests provide the highest level of specificity and accuracy for both carrier testing in relatives and for prenatal diagnosis. Assistive reproduction technologies such as pre-implantation genetic diagnosis are available to at-risk couples with known DNA mutations who wish to have children but for whom termination is not an option.
NTSAD has current information available on where to obtain the tests that are critical to the diagnosis and management of Sandhoff disease within families.
Sandhoff disease, like Tay-Sachs, is an autosomal recessive disorder but, unlike Tay-Sachs, occurs more commonly in the non-Jewish population. In fact, given the higher incidence of Sandhoff in non-Jews and the clinical similarity of the two diseases, it is probable that some of the non-Jewish children diagnosed before the availability of the laboratory tests actually had Sandhoff disease. In the moment that one receives a diagnosis, a line is crossed. One鈥檚 worldview is quite different from the moment before the diagnosis. In the new experience, the discussion of odds 鈥?whether one or will or will not get a disease, becomes irrelevant and individuals have a poignant, though usually unconscious, understanding of public health perspectives verses personal health issues. The public generally assumes that odds apply to individuals. Consumers do not experience the test, diagnosis, the day-to-day struggles, on a population level 鈥?it is completely personal. The affected family, individual, newborn uses their lived experience as the prism through which all life is assessed. |
