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X-linked hypophosphatemia (XLH), also known as hereditary type I hypophosphatemia (HPDR I) or familial hypophosphatemia, is an inherited, chronic condition that causes your body to lose phosphate.

About 80 percent of people living with XLH inherited it from one of their parents. If you have XLH, a doctor likely diagnosed the condition when you were a child. However, because this condition is rare, doctors can misdiagnose or miss the condition totally.

Though children and adults share some of the same symptoms, they can change as you get older. The following article looks at the symptoms you’re more likely to experience as an adult living with XLH.

Symptoms of XLH can vary. In most cases, symptoms appear within the first 18 months of age.

Research indicates that the rarity of the disease can lead to misdiagnosis or complete missed diagnosis, which can lead to poorer outcomes.

XLH in adults

If you have XLH, you may have noticed changes in symptoms over time. But, according to the Genetic and Rare Diseases Information Center, it’s also possible you received a diagnosis as an adult because you had no symptoms as a child.

If you do get a diagnosis as an adult, your symptoms may include:

  • joint pain
  • impaired mobility from enthesopathy (calcification of the ligaments or tendons)
  • tooth abscesses
  • periodontitis
  • hearing loss
  • muscle pain and weakness
  • limited range of motion
  • history of fractures

In addition, researchers have indicated that XLH can lead to other conditions, such as:

  • Hyperparathyroidism: occurs when the parathyroid gland is overactive and produces too much parathyroid hormone, which can eventually lead to too much calcium in the blood
  • Osteomalacia: softening of the bones
  • Enthesopathy: stiffness and pain in the ligaments and tendons that connect the bones to muscles
  • Osteoarthritis: a form of arthritis that causes joint stiffness and pain
  • Pseudofractures: formation of new bone growth over what looks like partial or incomplete fracture

Research has shown that XLH can have a significant impact on your quality of life as an adult, including affecting your mental health. However, research also shows that treatment may help improve your mental health as other symptoms improve.

XLH in children

In most cases of XLH, symptoms develop when you’re a child.

Your family or doctors may have noted early signs and symptoms of the condition. Some early signs include:

  • short stature
  • waddling or affected gait
  • slow growth rate
  • deformity in the limbs
  • bowing of the legs

The Genetic and Rare Diseases Information Center also adds that other early symptoms of XLH may include:

  • pain in the bones
  • dental pain or abscesses
  • muscle pain
  • rickets that doesn’t go away with vitamin D therapy
  • joint pain due to hardening of the ligaments or tendons
  • weakness in muscles
  • abnormal tooth development

Early treatment may help slow the progression of the condition and provide a better prognosis. However, if even if you didn’t receive a diagnosis during childhood, there are treatments that can help address some of the symptoms and improve quality of life.

Early diagnosis and treatment of XLH can improve quality of life. If you are living with XLH, you may already be using treatment that involves phosphate and vitamin D therapies.

A newer treatment option is burosumab (Crysvita). This medication works by targeting the hormones that lead to phosphate wasting. Clinical trials have shown this medication may improve growth and reduce pain and results suggest it as a first-line treatment.

Treatment can help stop existing problems from progressing and allow for more optimal growth and development in children. The main goal of treatment is to get more phosphate into the bloodstream, which will help prevent loss from the bones and teeth.

In some cases, your doctor may recommend surgery to help correct bone development. They will also likely recommend including your dentist as part of the treatment team to help keep dental issues from becoming a bigger problem.

Treatment should improve most physical symptoms, but a doctor may work with you to add medications to help manage pain. A doctor may also recommend mental health therapies to help you manage stress, anxiety, or depression.

There is no cure for XLH. However, researchers are continuing to examine XLH to learn more about the disease and develop better treatments.

Researchers are currently recruiting for a clinical trial to test if calcitriol alone will have an impact on XLH in both children and adults. They want to see if the lone medication will improve phosphate levels in the blood. This is a phase 1 trial, meaning there will be several more years before they will be able to prove their results.

If you’re interested in joining a clinical trial, you should talk to your doctor first. They can help determine if you’re a good match for a particular trial or advise against joining one based on other health conditions.

For more information on clinical trials, you can visit ClinicalTrials.gov.

If you are living with XLH, it may be passed on to your children.

According to the Genetic and Rare Diseases Information Center, your chances of passing XLH comes down to sex assigned at birth. Here’s how it breaks down:

  • if you’re male assigned at birth, there’s a 100-percent chance it will pass to your daughters and 0 percent chance it will pass to your sons
  • if you’re female assigned at birth, there’s a 50-percent chance it will pass to any of your children

The reason for the difference is that XLH affects the X chromosome. Having just one affected X chromosome will cause your child to develop the condition.

XLH can have varying symptoms for different people. These may include pain in the bones, joints, and muscles. It can also show through having a shorter stature and being more prone to dental issues.

The treatment for XLH has traditionally involved phosphate and vitamin D supplements, but new treatment options may better improve quality of life and response to interventions.