A retrospective study of the biochemical and radiological profile of children with genetic hypophosphatemic rickets and their response to conventional treatment

Abstract

Objectives: Assessing the biochemical and radiological profile of children with genetic hypophosphatemic rickets and their response to conventional treatment. Design: Retrospective descriptive study. Setting: Metabolic Bone clinic at Chris Hani Baragwanath Academic Hospital in Soweto, South Africa. Subjects: Children less than 18 years, attending the Metabolic Bone clinic from 1st January 2006 to April 2020, with genetic hypophosphatemic rickets, commenced on conventional treatment. Results: Seventy patients met the inclusion criteria. Majority of patients were black South African (n=54 (77%)). Positive family history seen in 32 (46%) patients. The patients were short statured with a mean height for age z score (HAZ) of - 3.4 ± 1.79. The mean calcium, phosphate, alkaline phosphatase, parathyroid hormone levels and median Thacher score was 2.3 ± 0.16 mmol/L, 0.84 ± 0.19 mmol/L, 776.6 ± 531 IU/L, 7.15 ± 4.8 pmol/L and 8 (4-8) respectively. Improvement on last follow up on treatment was seen in ALP (776 ±531 vs 525±232; p <0.001) and Thacher scores (8 (4-8) vs 2 (1-3.5); p =0.01) after 5 years, but no change in phosphate or HAZ. Conclusion: Conventional therapy for treatment of hypophosphatemic rickets is not associated with an improvement in HAZ despite an improvement in radiology and ALP. Adherence is a major challenge for the majority of patients.