OBJECTIVES: 1) The objective of this study was to explore radiological signs of intracranial and nuchal ligament calcifications in adult patients with X-linked hypophosphatemia (XLH) compared with controls and 2) to correlate signs of cranial calcifications in XLH patients with the presence of other extra-cranial enthesopathies, with the severity of skeletal XLH impact and with medical treatment during childhood.

SETTING AND SAMPLE POPULATION: Lateral and postero-anterior cephalograms from 36 adult XLH patients and 49 adult controls and X-rays from spine, pelvis, knees and ankles from 31 of the 36 XLH patients.

METHODS: Radiological signs of intracranial and nuchal ligament calcifications in XLH patients were compared with controls by Fischer's exact test. In XLH patients, the presence of cranial calcifications was correlated with the presence of other enthesopathies, with the severity of skeletal XLH impact and with medical treatment by Fischer's exact or chi-squared test.

RESULTS: Six (17%) XLH patients revealed major signs of intracranial calcifications. Nuchal ligament calcifications were common in XLH patients compared with controls (p = 0.018). Enthesopathy was present at 0-24 sites per XLH patient (median 2). Intracranial calcifications trended to correlate positively with vertebral enthesopathies (p = 0.059). Nuchal calcifications correlated positively with the severity of skeletal XLH impact (p = 0.040). Vertebral enthesopathies correlated negatively with medical treatment (p = 0.008).

CONCLUSION: More XLH patients than controls showed nuchal ligament calcifications, and some XLH patients showed intracranial calcifications. Severely affected XLH patients often had nuchal ligament calcifications. Medically treated XLH patients had few vertebral enthesopathies.