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RED FLAG SIGNS AND SYMPTOMS OF
X-LINKED HYPOPHOSPHATAEMIA (XLH) IN PAEDIATRIC PATIENTS

The diagnosis of XLH is frequently delayed, which has a detrimental effect on patient outcomes. 1
If you see a newborn or infant with a family history of rickets or a phosphate wasting disorder, consider referral. Other red flags for XLH include:

1. BOWING IN LOWER LIMBS

XLH can impair healthy bone mineralisation, leading to rickets and progressive lower limb deformities in children. Bowing deformities of the leg typically present during the second year of life, however, appropriate treatment can improve mobility and growth outcomes.

2. DELAYED WALKING WITH A WADDLING GAIT

XLH can impact motor development and mobility. During the second year of life, children with XLH typically present with delayed walking and an abnormal, or ‘waddling’ gait.

3. PAIN IN LEGS

Bone, joint and muscle pain are highly prevalent in children with XLH and frequently affect the lower limbs.

4. SHORT STATURE

In XLH, impaired limb growth with relatively preserved trunk growth results in disproportionate short stature. Decreased growth velocity is one of the main clinical symptoms of XLH.

5. ABNORMAL HEAD SHAPE

Craniosynostosis is a condition associated with XLH in which one or more of the fibrous sutures in a very young skull prematurely fuses by turning into bone. This may lead to an abnormal head shape in children.
THE ABOVE SIGNS AND SYMPTOMS MAY BE CAUSED BY XLH.
Consider referral to a paediatrician.
In the presence of red flag signs or symptoms, the following investigations and assessments can help confirm a diagnosis of XLH
FAMILY HISTORY
A positive family history can help confirm a diagnosis of XLH • Any first-generation family member of a patient with XLH should be investigated for XLH; sons of males are not affected • Mutational analysis of the PHEX gene can help in cases with a negative family history (approx. one-third of patients)
PHYSICAL EXAMINATION
A detailed clinical evaluation should include evidence of: • Rickets • Growth failure • Dental abnormalities • Craniosynostosis
RADIOLOGICAL EXAMINATION
• Consider performing radiography of the knees and/or wrists and/ or ankles to confirm a diagnosis of rickets1 RED FLAG FINDINGS • Rickets characterised by cupped and flared metaphyses and widened and irregular physes (growth plates) of the long bones