Diagnosis of XLH

Early and accurate diagnosis of X-linked hypophosphatemia (XLH) is important so that the condition can be managed.

Diagnosis of XLH is typically during childhood, usually 1-2 years of age, when legs start supporting weight. In some instances, adults with XLH may be misdiagnosed during childhood or can remain undiagnosed.


Watch video

During early childhood, you can recognize common symptoms of XLH such as:

  • Impaired growth and short stature
  • Outward curving of the legs, also known as bowed legs, 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 condition.

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 condition as:

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

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


ENDOCRINOLOGIST specializes in treating disorders that affect hormones.

NEPHROLOGIST specializes in treating disorders that affect the kidneys.

RHEUMATOLOGIST specializes in treating disorders that affect the joints and muscles.

MOLECULAR GENETICIST specializes in treating genetic disorders.

Your care team can include other professionals:

DENTISTS can help manage oral care as teeth can be more prone to infection with XLH. Regular check-ups and establishing a plan with your dentist can help prevent recurrent teeth infections.


PHYSICAL THERAPISTS can help you strengthen your muscles and teach you how to properly exercise to avoid injury.


OCCUPATIONAL THERAPISTS can help you fine tune your movement to optimize daily activities such as showering and cooking.

Find an XLH specialist near you


It’s not easy to remember everything your healthcare professional 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 symptom management will be for you and/or your child.

At appointments, your doctor may:

  • Ask questions about family history of symptoms associated with XLH
  • Obtain labs, such as blood and urine samples
  • Obtain X-ray to evaluate the condition of the bones
  • Recommend genetic testing to help confirm a diagnosis of hypophosphatemia
  • Discuss ways to manage the symptoms of XLH

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

Common misdiagnoses for XLH: rickets

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

Common misdiagnoses for XLH: bowed legs

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

Common misdiagnoses for XLH: hypophosphatasia

Hypophosphatasia, a condition that also affects bones and teeth


Early and accurate diagnoses are key to improved symptom management

See the signs and symptoms of XLH in children