A 7 year-old twin girl with hypophosphataemic rickets was evaluated for a recent onset of mild strabismus.
She was a homozygous twin sister with hypophosphataemic rickets diagnosed at the age of 2 years, with a mutation in intron 21 of the PHEX gene, which was also present in her sister.
The girls’ clinical histories were remarkable for an important lower limb varus that progressively improved after starting phosphate supplementation with a galenical solution (Joulies solution 1 mmol phosphate/ml) and vitamin D 1,25 OH.
During the examinations, both girls were in good general condition. Physical examinations were unremarkable, except for tibial varus, bilateral fifth finger clinodactyly and bilateral syndactyly of the third and fourth foot fingers. No major head shape abnormalities were noticeable except for a high forehead.
One patient presented with a slight strabismus, normal isochoric isocyclic and reactive pupils, no signs of cranial nerve deficit, and no alterations in the rest of the neurological examination. An ophthalmological evaluation showed bilateral papilloedema. A cerebral MRI scan was then performed, suspecting elevated intracranial pressure (figure 1). The same examination was performed on the asymptomatic sister which also demonstrated papilloedema with similar findings on cranial MRI too.
Which is the most likely diagnosis?
How should these patients be managed?
Third to fourth ventricle cystostomy
Wait and see with periodical visual evoked potential follow-up
How should patients with X linked hypophosphataemic rickets (XLH rickets) be managed for the risk of craniosynostosis?
Monitor cephalic anthropometric measures
Perform a MRI scan if clinical signs of craiosynostosis or intracranial hypertension are present
Perform a skull X-ray every 2 years
Perform an MRI scan every 2 years
Answers can be found on page 02.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Parental/guardian consent obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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