Treatment of hypophosphataemic rickets in children remains a challenge

Abstract

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

Material and methods: 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.

Results: 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.

Conclusion: 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.