Table 1 Summary of recommendations for the follow-up of patients with XLH

From: Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia

Examination

0–5 years

5 years to start of puberty (9–12 years)

Puberty

Transition to adult care

Adult

Frequency of visits

1–3 months

3–6 months

3 months

6–12 months

Height, weight, BMI

Every visit

IMD and ICDa

Every visit

Yearly

Head circumference, skull shape

Every visit

Not required

Rickets, osteomalacia, pain, stiffness, fatigue

Every visit

Every visitb

Musculoskeletal function, 6MWTc

Not feasible

Yearly

At least once

Yearly

Orthopaedic examination

Once a year in presence of substantial leg bowing

At least once

Yearlyd

Dental examination

Twice yearly after tooth eruption

Twice yearly

Every visit

Twice yearly

Hearing test

Not feasible

From 8 years if symptoms of hearing difficulties

Serum total or bone-specific ALP, calcium, phosphate, PTH, creatinine, eGFRe

At least every 3 months

Every visit

25(OH) vitamin D

Yearly

Urine calcium to creatinine ratiof

Every 3−6 months

Fasting (in adults) serum phosphate and TmP/GFR

Every 2 weeks during the first month, every 4 weeks during the following 2 months and thereafter as appropriate in patients on burosumab treatment (ideally 7–14 days after injection)

1,25(OH)2 vitamin D

At least every 12 months in patients on burosumab treatment

Blood pressure

Twice yearly

Renal ultrasound

Every 1–2 years in patients on phosphate and active vitamin D and in patients on burosumab with pre-existing nephrocalcinosis

Left wrist and/or lower limb radiographs

If insufficient clinical response to therapy in children; if leg bowing does not improve in growing patients; in the case of short stature (bone age assessment); in the case of orthopaedic surgery; in the case of persistent bone pain in the pelvis or legs

Dental orthopantomogram and/or cone beam CT

Not feasible

Based on clinical need starting at the age of 6 years

Fundoscopy and brain MRI

If suspicion of craniosynostosis, headache, neurological symptoms

If recurrent headaches, declining school and/or cognitive performance and/or neurological symptoms

Spine MRI

Not required

If symptoms of spinal stenosis or persisting back pain

Cardiac ultrasonographyg

In the case of persistent elevated blood pressure (>95th percentile)

Quality of lifeh

Not feasible

Every 2 years (if available)

  1. ALP, alkaline phosphatase; BAP, bone alkaline phosphatase; eGFR, estimated glomerular filtration rate; ICD, intercondylar distance; IMD, intermalleolar distance; TmP/GFR, maximum rate of renal tubular reabsorption of phosphate normalized to glomerular filtration rate; 6MWT, 6-min walk test. aSee Sass and Hassan151 for reference values. bAlso search for pseudofractures, osteoarthritis and enthesopathy. cIf available, see Saraff et al.152 for reference values. dIn symptomatic patients. eUse the Schwartz formula in children, Modification of Diet in Renal Disease or Chronic Kidney Disease Epidemiology Collaboration equation in adults153. fIn patients with very low urinary creatinine levels, for example, owing to low muscle mass, 24-h urine collection is recommended to assess urinary calcium excretion. The upper normal range of the urinary calcium-to-creatinine ratio (mol/mol) for different age groups is as follows: <1 year, 2.2; 1–3 years, 1.4), 3–5 years, 1.1; 5–7 years, 0.8; 7–18 years, 0.7; >18 years, 0.57. Detailed age-related normal ranges for urinary calcium and phosphate-to-creatinine ratios in children can be found in Pott et al.29 and a web calculator to calculate age-adjusted z-scores is available32. The upper normal limit of 24-h urinary calcium excretion is 0.1 mmol (4 mg) per kg body weight for all adults or 6.2 mmol (250 mg) in female adults and 7.5 mmol (300 mg) in male adults154. gAccording to international guidelines. hUsing age-appropriate and disease-appropriate quality-of-life scales.
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