Symptoms of XLH

X-Linked Hypophoshpatemia (XLH) is caused by one of several mutations of the PHEX gene, all of which cause XLH.  There does not seem to be any correlation between the specific mutation and the severity of the symptoms experienced.  Those with XLH generally exhibit the following:  

  • Abnormal bone and tooth development, which may range from mild or moderate to severe.
  • Rickets that resists traditional Vitamin D therapy.

A few people with XLH exhibit no bone-related symptoms, and a study published in 1994 notes that it’s not uncommon for XLH to go undiagnosed in those with mild to moderate symptoms.  Our experience with XLH Network members is that this continues to happen today.  In fact, we hear from many adults with fairly severe symptoms who, because the disorder is uncommon, were only recently correctly diagnosed as XLH.  

Symptoms vary

It's not uncommon for XLH to not be recognized right away, or to be discounted, and many will recognize their own experience in the following discussion, but primarily the symptoms of XLH may include the following:

  • Lower limb deformities (bow or knock-knee)
  • Waddling gait
  • Short stature or declining growth rate
  • Spontaneous tooth abscesses
  • Bone pain
  • Muscle pain and weakness

The symptoms of XLH tend to appear when a child begins to bear weight on his or her legs. In a very young child (8-16 months), parents may notice bowing and/or twisting of the lower legs, or knock-knees in some. A pediatrician may remark on the child's pronounced or “bossed” forehead while at the same time discounting the bowing as an effect of bulky diapers or assure the parents that the child will outgrow it....without doing any testing to make sure there's no problem.

The child's wrists may be thicker than they should be, and when examined, the child's chest may have an array of bony beads, often called a rachitic rosary. Teeth may be slow to appear, and the child may be very small for his or her age.

Rarely, there may be a problem with bone development in the head, and the physician should be able to recognize this development called craniosynostosis very quickly when measuring the size of the child's head.

As the child grows older and starts walking, parents may not recognize an abnormality in the child’s gait, but relatives or acquaintances who are only in infrequent contact may express concern.

The child's small stature may also be increasingly noticeable compared with his or her peers. Dental abscesses are a common complaint once teeth erupt because of faulty formation inside the tooth – not decay or trauma – and some children may feel different degrees of pain in their legs.

Doctors may use the term rickets, when they consider this collection of symptoms in children.  But it's important to know what the cause is for the child's rickets, as successful treatment depends on a correct diagnosis.  Standard vitamin D therapy works well for those who develop rickets due to not getting enough vitamin D in their diet or not getting enough exposure to sunlight, but it would be a waste of time in someone with XLH.  Appropriate testing to rule out phosphate wasting will show whether standard vitamin D therapy would be appropriate, or whether XLH or another disorder is what's actually causing the symptoms.

Source: The XLH Network Board of Directors

© The XLH Network Inc.
The authors of this web site are not medical professionals, and this information does not substitute for medical care. Information on these pages is based on biomedical research, published in peer-reviewed journals, and international research conferences. Additionally, in some cases anecdotal information is provided by subscribers to a mailing list and/or members of a forum for The XLH Network Inc. A listing of XLH research is available. Please read our full disclaimer

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Last modified Aug 13, 2017

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