Diagnosis of XLH

Elizabeth and her mother, Jean, living with XLH

Early and accurate diagnosis of XLH is important so that the disease can be managed. Diagnosis of XLH is typically during childhood, usually within 1-2 years of age, when legs start supporting weight. During this time, you can also recognize common symptoms of XLH such as:

  • Impaired growth and short stature
  • Outward curving of the legs, also known as leg bowing, when a child is in a standing position
  • Knock-knees, a condition when both the knees are at an angle touching each other
  • Bone, muscle and joint pain
  • Dental abscesses, which appear as small, pus-filled ulcers in the gums
  • Waddling gait while walking
  • Enlargement of wrists and knees
  • Misshapen head

The earlier XLH is identified, the better the chances are of managing the symptoms and, therefore, the disease.

In some instances, adults with XLH may be misdiagnosed during childhood or can remain undiagnosed. They may continue to experience unresolved symptoms of their ongoing disease, such as:

  • Bone pain
  • Joint pain and stiffness
  • Fractures and pseudofractures
  • Early onset of osteoarthritis
  • Dental abscesses
  • Fatigue and weakness

—Melissa, XLH patient

Diagnosing XLH can be tricky because it is a rare disease. It is important that you find doctors who are knowledgeable about XLH and can identify and manage the disease. These specialists are often found at university medical centres and specialize in metabolic bone disorders.

An endocrinologist is a specialist in treating disorders affecting hormones

Endocrinologist (adult/pediatric)
Specializes in treating disorders that affect hormones

A nephrologist is a specialist in treating diseases of the kidneys

Nephrologist (adult/pediatric)
Specializes in treating diseases that affect the kidneys

A molecular geneticist is a specialist in treating genetic diseases

Molecular geneticist
Specializes in treating genetic diseases

It’s not easy to remember everything your health care provider will tell you during your visit. Keeping a diary to record symptoms, appointment dates, notes about medicines, and even jotting down questions you might have can help you keep track of the information you receive. The more engaged you are, the easier the diagnosis process and disease management will be for you and/or your child.



At your appointments, your doctor may:

Family history and inheritance of XLH

Ask you questions about your family history of symptoms associated with XLH

Laboratory tests are required for the diagnosis of XLH

Ask to complete laboratory tests requiring blood and urine samples to understand the levels of phosphate in the body and X-rays to evaluate the condition of the bones.

Use genetic testing to diagnosis hypophosphataemia

Use genetic testing to help confirm a diagnosis of hypophosphataemia

Prescription medicine to treat XLH

Following your initial diagnosis, your doctor may prescribe treatments that can help improve the symptoms of XLH

Because XLH is a rare disease that affects anywhere from 1 in 20,000 to 1 in 25,000 people, it can be mistaken for other diseases, such as:

XLH can be mistaken for other types of rickets

Nutritional rickets and other types of rickets disorders that can be inherited

XLH can be mistaken for normal variations in leg appearance

Normal variations in the appearance of the legs (physiologic leg bowing)

XLH can be mistaken for hypophosphatasia

Hypophosphatasia, a disease that also affects bones and teeth