What Are My Reproductive Options if I Have Mitochondrial Disease?
Mitochondria are the “powerhouses” of a cell, producing most of the energy that cells need to function.
In mitochondrial disease, of which there are many types, these cellular compartments cannot function properly. Because almost every cell has mitochondria, mitochondrial disease can affect every system in the body.
If you or your partner have mitochondrial disease, it’s a good idea to discuss family planning with your doctor and genetic counselor. They can help to determine your risks of transmitting the disease to your children. They can also advise on the reproductive options that are available to you to avoid this risk.
DNA and mitochondrial disease
Most of the genes that are necessary to support mitochondrial function reside within the cell nucleus. However, a small number of genes are maintained within the mitochondria themselves. A mutation in any one of these 37 genes can cause mitochondrial disease.
During reproduction, children inherit one copy of their genes from their mother, and one copy from their father. (We all have two copies of each gene.) However, they inherit their mitochondria and the genes they carry, primarily from their mother. In extremely rare cases, a child has inherited paternal mitochondria as well.
This separation of mitochondrial and cellular DNA means that if a child’s father has mitochondrial disease due to a gene contained in the mitochondria, it is very unlikely his children will inherit the disease. However, if the mother has a genetic mutation in the mitochondrial genome, all of her children are likely to inherit the disease.
If the mutations are in genes that reside in the nucleus of the cell, however, the mother or the father are equally likely to transmit the disease to their children. Depending on the inheritance pattern of the specific mitochondrial disease a parent has, the disease can be passed in a recessive or dominant manner.
In vitro fertilization and pre-implantation genetic diagnosis
In vitro fertilization (IVF) is act of combining a sperm and egg in a test tube or dish to create an embryo that can be implanted into the mother. Doctors can screen embryos resulting from in vitro fertilization before transferring them to the mother’s uterus. This screening is called pre-implantation genetic diagnosis (PGD). Doctors only implant embryos that show no evidence of genetic disease. In this way, parents with such diseases can have children genetically related to both of them, but who do not carry disease-causing mutations.
When the mutation is in the nucleus
If you or your partner have a mitochondrial disease caused by a mutation in a gene located in the cell nucleus, you can opt for IVF followed by PGD to screen for healthy embryos.
If you have mitochondrial disease with a recessive inheritance pattern (meaning that both gene copies must have a disease-causing mutation to cause the disease), and your partner is not a carrier, your children will be carriers of the disease, but should not have symptoms. But if your partner has a copy of a disease-causing mutation (is a carrier), then your children have a 50% chance of being carriers and a 50% chance of inheriting two copies of a disease-causing mutation and developing the disease. This means that, during the creation of embryos via IVF, half of these embryos will be carriers only and suitable for implantation.
If you or your partner has a dominant mitochondrial disease (meaning one gene with a disease-causing mutation is enough to cause disease), then your children will have a 50% chance of inheriting the disease. Again, after IVF, doctors screen the embryos and only implant those without the mutation.
When the mutation is in mitochondria
When a mitochondrial disease-causing mutation resides in a gene in the mitochondria, IVF using a donor egg is an option. Here doctors use the father’s sperm to fertilize the donor egg, which does not carry a mutation in the mitochondria. They then implant the embryo in the mother’s uterus. The embryo that results is generically related only to the father.
Another option is mitochondrial donation IVF. Here, doctors collect the mother’s egg and transplant its nucleus into a donor egg from which they removed the nucleus. They then allow the father’s sperm to fertilize the egg. The resulting embryo should contain only mitochondria from the donor egg. The embryo created using this method will be genetically related to both parents, but will only have mitochondrial DNA from the donor egg.
If the father is the one with the mitochondrial disease, no precautions may be necessary. This is because it is very rare for paternal mitochondria to be transmitted to the embryo. Rare cases of this are known to occur. However, the vast majority of the mitochondria in the embryo come from the mother’s egg. A genetic counselor and doctor specializing in IVF can discuss with you the risks of transmitting paternal mitochondrial disease to your children.
Are there risks?
Every medical procedure has risks. These are different for every patient, so it’s important to discuss with your doctor the specific risks to you before going ahead with a procedure.
In the case of mitochondrial donation IVF, it is possible that some mutated mitochondria may be transferred together with the nucleus to the donor egg. Researchers are working on refining the technique to improve transfer, and reduce the risk of contamination from the mother’s mitochondria.
IVF is an expensive technique and not all health insurance plans cover it. It also can take multiple attempts to achieve pregnancy through IVF.
Last updated: April 21, 2020
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