X-linked hypophosphatemia (XLH) is a rare, progressive genetic disorder that is characterized by excess excretion of phosphate by the kidneys. Since phosphate is an important mineral required for healthy bones, teeth, and other body functions, loss of phosphate can lead to rickets-like symptoms such as osteomalacia (soft and weak bones), early osteoarthritis, fractures, pain, dental abscesses (buildup of pus in the teeth), and stunted growth.

What is genetic counseling?

Genetic counseling is the process of helping people with genetic diseases understand the implications of the disorder and the likelihood of it being passed to next generations.

Genetic counselors are members of a multidisciplinary healthcare team; they are specialists who have received advanced training in medical genetics.

Genetic counselors are a connection between the physician and the patient. They help in making informed choices by analyzing disease inheritance patterns and results of genetic tests, and providing advice on family planning. They also are a source of emotional support for people affected by a genetic disease.

Why genetic counseling is important for XLH?

Although about 20–30% of XLH cases occur due to spontaneous mutations with no previous family history, in most cases, the disease is inherited from the parents. The cause is a mutation in the PHEX gene that is situated on the X-chromosome. The disease is inherited in a X-linked dominant manner and can affect both girls and boys.

Genetic testing for mutations in the PHEX gene is an important diagnostic tool to confirm XLH. These mutations affect the activity of another gene called FGF23, which ultimately promotes excess phosphate excretion by the kidneys.

A thorough investigation of family history is very important in determining the probability of future generations inheriting the disease because it varies depending on which of the parents is affected. A man affected by XLH will pass the disease to all his daughters, but not his sons, whereas a woman with XLH has a 50% chance of passing it to any of her children.

Consequently, genetic counseling is very much needed in XLH to allow patients and their family members to make informed decisions about family planning.

Genetic counseling before XLH diagnosis

Results from urine tests, blood tests, and X-ray imaging can make a clinician suspicious about the presence of XLH. In such cases, the patient may be referred to a genetic counselor to assess the need for a genetic test. This is called pre-test counseling. Pre-test counseling can help patients understand the risks, limitations, and benefits of the genetic test, and gives them enough time to make informed decisions.

Genetic counseling after XLH diagnosis

If a diagnosis of XLH is confirmed by genetic testing, patients have the option to consult a genetic counselor for advice on the next course of action.

The genetic counselor reviews the test results and correlates them with the patient’s family history to determine the likelihood of the disease affecting future children. If required, affected individuals may be apprised of the possibility of in vitro fertilization with pre-implantation genetic diagnosis that screens embryos for genetic disorders before being placed in the mother’s womb.

Throughout the process, genetic counselors provide patients with moral and emotional support. They also can direct them to support groups to help  cope with the disease and its implications.


Last updated: Jan. 6, 2020


XLH News Today 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 providers 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.

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Özge has a MSc. in Molecular Genetics from the University of Leicester and a PhD in Developmental Biology from Queen Mary University of London. She worked as a Post-doctoral Research Associate at the University of Leicester for six years in the field of Behavioural Neurology before moving into science communication. She worked as the Research Communication Officer at a London based charity for almost two years.