Carriers & Reproductive Choices
RTD IS AN AUTOSOMAL RECESSIVE GENETIC CONDITION
Genetic means it is inherited. Recessive means the genetic error sits on a non-dominant gene; we have two copies of each gene, so carriers of a recessive gene who have a healthy copy are unaffected. Autosomal means the affected gene is located on a non-sex chromosome (of the 23 pairs of chromosomes we have, 22 are autosomal). Both men and women can carry the mutated gene and boys and girls can get the disease.
Most people have two functioning copies of both the SLC52A2 and SLC52A3 genes. People with one faulty copy and one functioning copy of either the SLC52A2 or SLC52A3 gene are called “carriers.”
Even though carriers don’t have RTD themselves, they can still pass the faulty gene on to their children.
Approximately 1 in 1000-4000 people is a genetic carrier for RTD. Most have no idea they are carriers until they have a child born with RTD.
How RTD is Inherited
RTD is a recessive disease, which means that, generally, a child or adult will only develop RTD if both parents pass on the SLC52A2 or SLC52A3 mutated gene.
When two parents are carriers, there is:
A 25% chance that their child will be unaffected
A 50% chance that their child will be a carrier
A 25% chance that their child will have RTD
If only one parent is a carrier, the child is usually not at risk for RTD (though they do have a 50% risk of being a carrier). However, in very rare cases, mutations in the SLC52A2 or SLC52A3 genes can occur during egg or sperm production. In this situation, only one parent will be a carrier of the SLC52A2 or SLC52A3 mutations. In addition, a small percentage of carriers have a mutation that cannot be identified through current testing. In this case, it will appear as though the disease has been caused by a single carrier.
A DNA test is the only way to detect carrier status. The DNA test is a simple procedure, based on a small blood draw. Deciding whether or not to undergo genetic testing is highly personal, and we strongly recommend discussing it with a physician or genetic counselor. Usually, the testing is only recommended—and only covered by insurance—for those known to be at risk for genetic diseases. Carrier screening via saliva is also available as an alternative to a blood draw.
For couples who are carriers, reproductive decisions can be sensitive. A number of options are available, such as adoption, prenatal testing, and pre-implantation genetic diagnosis (PGD). PGD screens embryos for genetic disorders and selects the unaffected embryos for implantation.
Cure RTD believes that your family has the right to choose whatever option is best for your own values. We help families understand their options and provide resources to support their decision-making process. We do not advocate any specific course of action, nor do we pressure families to choose one way or the other.
We encourage each family to discuss their situation with a physician, genetic counselor, and—if helpful—a therapist or a spiritual advisor.