ESPE Abstracts

Background: The goal of treatment in children with hypophosphatemic rickets (HR) attempts to correct growth and leg deformities. However, growth is compromised despite treatment and patients are at risk of developing nephrocalcinosis in the future. Some factors (sex, age and height at diagnosis) have been related to height outcome, but little is known about the impact in growth of different dosage of treatment or alkaline phosphatase (ALP) levels.

Objective and hypotheses: 1) To evaluate growth improvement in relation to: doses of phosphate, calcitriol and the decline of ALP. 2) To assess the relation between dose and duration of treatment with the incidence of nephrocalcinosis.

Method: Retrospective review of patients with HR (2006–2016). Patients were divided as responders in G1: height improvement >0.5 S.D.; G2≤0.5 S.D. We evaluate improvement in relation to sex, age and height at diagnosis, treatment dose and ALP.

Results: Nine children were identified. The children improved their height 0.5 S.D. (−0.04, 0.65) after 4.4 years (3.9–8.0) of treatment. Eight children had a Z score-height ≤−2 S.D. (−2.9 S.D.), and were below their midparental height (−1.8 in relation to MPH). Genu varus was present in all children and improved in 66% of them. There were no differences in phosphate dose (G1 68.5 vs G2 70 mg/kg per day) or calcitriol dose (25.7 vs 23.4 ng/kg per day) between groups. After treatment, ALP decreased more in G1, but it did not reach statistical significance (P=0.41). Five children developed nephrocalcinosis and tended to need higher phosphate doses, lower calcitriol doses, longer duration of treatment, and had a higher ALP at the last visit (P=0.048).

Conclusion: The children improved their growth but remained below their MPH at the last visit. We can not identify a treatment protocol associated with better height outcome. Children with nephrocalcinosis had ALP higher at the last visit, which could reflect a more aggressive phenotype.