Treatment of hypophosphataemic rickets in children remains a challenge

Hypophosphataemic rickets (HR) is a rare hereditary disease characterised by hypophosphataemia, defects in bone mineralisation and rickets.

We searched the hospital files at H.C. Andersen Children's Hospital, Odense University Hospital, Denmark, for children with the International Classification of Diseases 10 codes E83.3B (vitamin D resistant rickets) and E83.3A1 (familiar hypophosphataemia) from 1 February 2012 to 1 May 2012. Data were collected retrospectively.

Fifteen HR children were identified. X-linked hypophosphataemia with mutations in the phosphate-regulating endopeptidase homologue, X-linked were present in 80%; three had autosomal recessive HR with dentin matrix protein mutations. The children were treated with phosphate and alphacalcidol for an average of 7.7 years ± 5.1 standard deviations (SD). At the latest follow-up, the mean age was 10.1 (+5.4) years, and the mean height had declined 0.8 SD from the first contact. A total of 40% had an actual height below -2.0 SD, and 40% underwent surgery for leg deformities. Among the medically treated patients, five had genu varus with a mean medial femoral condyle distance of 6.6 cm (+ 2.79), and two patients had genu valgus with a mean medial malleolus distance of 12.3 cm (+ 1.77). Episodes of secondary hyperparathyroidism were seen in 87%, and one patient developed transient nephrocalcinosis.

The current medical treatment for HR is insufficient. The rarity of the disease and the treatment difficulties of HR call for centralised management. International multi-centre trials including novel treatment options are warranted.