Table 1.
Initial evaluation of common and rare complications of XLH
| Evaluation | Age of patient | ||
|---|---|---|---|
| <5 years | 5–18 years | Adults | |
| Clinical | |||
| Growth chart | ✓ | ✓ | ✓ |
| Signs of rickets and/or leg deformity | ✓ | ✓ | ✓ |
| Measure IMD and ICDa | ✓ | ✓ | ✓ |
| Head circumference and skull shape | ✓ | ✓ | NA |
| Neurological examination (for consequences of craniosynostosis and spinal stenosis) | ✓ | ✓ | ✓ |
| Hearing assessment | NA | ✓ | ✓ |
| Dental and oral examination | ✓b | ✓ | ✓ |
| Musculoskeletal function (gait)77 | NA | ✓ | NA |
| Biochemistry | |||
| Blood: calcium, phosphate and creatinine | ✓ | ✓ | ✓ |
| Spot urine: calcium, phosphate and creatininec | ✓ | ✓ | ✓ |
| TmP/GFRd (refs59,193) | ✓ | ✓ | ✓ |
| Estimated GFR194,195 | ✓ | ✓ | ✓ |
| 25(OH) vitamin D | ✓ | ✓ | ✓ |
| 1,25(OH)2 vitamin D | ✓ | ✓ | ✓ |
| PTH | ✓ | ✓ | ✓ |
| ALP (children) and BAP (adults) | ✓ | ✓ | ✓ |
| Intact FGF23 (in case of negative family history) | ✓ | ✓ | ✓ |
| Imaging | |||
| Wrist and/or knee and/or ankle radiographs (rickets) | ✓ | ✓ | NA |
| Standardized, well-positioned anterior–posterior standing limb alignment radiograph (using low-dose techniques if possible)e | ✓ | ✓ | ✓ |
| Dental orthopantomogramf | NA | ✓ | ✓ |
| Brain MRIg | ✓ | ✓ | ✓ |
| Renal ultrasonography (nephrocalcinosis) | ✓ | ✓ | ✓ |
ALP, alkaline phosphatase; BAP, bone alkaline phosphatase; FGF23, fibroblast growth factor 23; GFR, glomerular filtration rate; ICD, intercondylar distance; IMD, intermalleolar distance; NA, not applicable; PTH, parathyroid hormone; TmP/GFR, maximum rate of renal tubular reabsorption of phosphate per glomerular filtration rate; XLH, X-linked hypophosphataemia. aPatient standing with weight on both feet and feet hip-width apart; alternatively, patient lying down. Reference values are given elsewhere73. bStarting at 3 years of age. cUpper normal range of calcium:creatinine ratio (mol/mol): 2.2 (<1 year), 1.4 (1–3 years), 1.1 (3–5 years), 0.8 (5–7 years) and 0.7 (>7 years). dNormal range in infants and children (6 months to 6 years): 1.2–2.6 mmol/l; adults: 0.6–1.7 mmol/l (refs59,193); a web calculator is found elsewhere194. eLow irradiation system (for example, EOS) and check for pseudofractures in adults. fOn the basis of clinical needs. gIn the presence of a skull morphology in favour of craniosynostosis or clinical signs of increased intracranial pressure (for example, persistent headache or vomiting).