If you have phenylketonuria (PKU), you may be wondering whether you can pass the disease on to your future children.
Here is more information about how children inherit PKU and your risk of passing the rare genetic disorder to the next generation.
What causes PKU?
PKU is caused by a genetic mutation in the PAH gene. The PAH gene resides on chromosome number 12 and contains the instructions necessary to make the phenylalanine hydroxylase enzyme. This enzyme is responsible for converting the amino acid called phenylalanine into another amino acid, tyrosine. Amino acids are building blocks of proteins.
When the phenylalanine hydroxylase enzyme does not function properly, phenylalanine builds up in the body. Levels of tyrosine also become low. These two factors both contribute to the symptoms of PKU.
How do children inherit PKU?
The human body contains 23 pairs of chromosomes. Children receive one copy of each chromosome from their mother and the other from their father. Among those 23 pairs of chromosomes, one pair are sex chromosomes and determines the gender of the child. The other 22 are autosomes. PKU is inherited in an autosomal recessive pattern. This means that a child needs to inherit a faulty copy of the PAH gene from both of the parents to develop the disorder.
If you have PKU, the risk of having a child with the disease will depend on the genetic status of your partner. If your partner also has PKU, then all of your children will have the disease. This is because both you and your partner only have faulty copies of the PAH gene to give to your children.
If your partner does not have PKU and is not a carrier of the disease, none of your children will have PKU. They will, however, all be carriers of the disease because they will have inherited one faulty copy of the PAH gene. This means that they will have a risk of passing the mutated gene onto their own children.
If you have PKU and your partner is a carrier of the disease — meaning your partner has one healthy and one faulty copy of the PAH gene — then your children will have a 50% chance of having the disease and a 50% chance of being a carrier.
Things to consider before having children
The odds of having a child with PKU, if you have the disease, are largely dependent on your partner’s genetic status. Thus, it is important that your partner has genetic testing to find out whether or not he or she is a carrier of the disease. Following the test, you and your partner should speak with a genetic counselor about the odds of having an affected child.
You and your partner also may want to consult with a genetic counselor about the possible reproductive options that may be available to you.
Last updated: Feb. 11, 2021
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Phenylketonuria News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.