We understand that having a rare genetic condition can throw up all sorts of questions about the future.
To help you think through your options we have described how XLH passes from parent to child, and outlined some aspects to consider when the time comes to have a family.
Genetics
X-linked genetic disorders are caused by genes on the X chromosome.
Genetic transmission refers to the passing of genetic traits or disorders from one generation to the next through genes. XLH is an X-linked dominant disorder caused by a dominant gene located on the X chromosome.
X and Y are the sex chromosomes, and they specify whether a person is female (usually XX) or male (usually XY). Genetic disorders with an X-linked inheritance pattern affect males and females differently.
In X-linked dominant disorders, a single copy of the mutated gene on one of the X chromosomes is sufficient to cause the disorder in both males and females. This means that if a person inherits the mutated gene from either their mother or father, they will have the disorder.
So, if you are a female with XLH there is a 50/50 chance that children of either sex will have XLH. If you are a male with XLH, your daughters will definitely inherit XLH, but your sons will not.
If you wish to learn more about genes and genetic transmission we recommend this site https://learn.genetics.utah.edu/
Pregnancy
During pregnancy, it’s essential to monitor and adjust vitamin D levels, considering phosphate supplements if needed. Pregnant women already on active vitamin D and phosphate supplements may continue it. Burosumab is not recommended if you are pregnant or think you may be pregnant. There is not enough experience to know if burosumab may harm your unborn baby.
Breastfeeding is recommended for new mothers. There is not enough experience to know if burosumab passes into your breast milk. If you are breastfeeding please consult your specialist for treatment advice.
Pregnant women may experience additional pain throughout pregnancy, due to the additional demands on the body. It is recommended that patients with rare bone conditions should receive close surveillance by healthcare professionals, beginning at preconception.
Family planning and IVF
In-vitro fertilisation (IVF) can be used to avoid passing on a genetic condition. Pre-implantation genetic testing for monogenic or single-gene disorders (PGT-M), previously known as pre-implantation genetic diagnosis (PGD), is a type of embryo testing that can be used by people with serious inherited conditions in their family. Only embryos that have been tested and found to be free of the condition are placed back into the woman’s womb.
The Human Fertilisation and Embryology Authority in the UK recognises that XLH is a serious inherited condition and has approved XLH for PGT-M. Please raise this with your GP and ask to be referred to a genetic counsellor if would like to discuss this further.
Amy’s story
As part of our series of videos from those with lived experience of XLH, we asked Amy about the choices she made when starting a family. Amy has XLH and chose IVF as a way to ensure that her two girls were not carrying the XLH gene.
You can listen to Amy’s story in the video below. XLH UK would like to thank Joe Bonnell and Rachel Lewis for their expertise in the making of this video.