Efficacy of Burosumab Every 2 Weeks in an Adult with X-Linked Hypophosphatemia: Should We Learn from Children?

X-linked hypophosphatemia is a genetic condition that leads to fibroblast-growth-factor 23 (FGF23) increase, causing phosphate renal wasting. Since 2018, burosumab, an anti-FGF23 antibody, has been used for this disease with different dosage in children and adults. We report the case of burosumab administration every 2 weeks, as usually done in children. We retrospectively evaluated parathormone (PTH), alkaline phosphatase, serum phosphate, tubular reabsorption of phosphate (TRP), and 25OH vitamin D every 2 weeks in a 29-year-old man with nephrocalcinosis and tertiary hyperparathyroidism who did not respond to standard treatment with burosumab nor to maximum dosage and was treated with burosumab 90 mg every 2 weeks. His serum phosphate and TRP increased with this regimen compared with 4 weeks frequency (respectively 1.74 ± 0.26 mg/dL vs. 2.3 ± 0.19 mg/dL [p 0.0004] and 71.3% ± 4.8% vs. 83.9% ± 7.9% [p 0.01]) with decrease in PTH (183 ± 24.7 pg/mL vs. 109 ± 12.2 pg/mL [p 0.04]). Burosumab may be a good choice in adult patients with X-linked hypophosphatemia; new data are needed regarding the increase in dosage and/or frequency of administration as usually done in children, to achieve disease control.

Evaluation of Renal Function and Scars in Children With Primary Vesicoureteral Reflux.

OBJECTIVE: To evaluate growth, glomerular and tubular function, renal damage, scars in children affected by primary VUR. METHODS: We retrospectively evaluated the clinical records of our Unit from January 2006 to September 2020. For each patient we evaluated growth, laboratoristic and scintigraphic glomerular and tubular function, renal damage and collective system urodynamics at baseline and at the last visit. RESULTS: We enrolled 41 patients affected by primary VUR and treated with continuous antibiotic prophylaxis. Glomerular function and urodynamics did not change over time. EFNa directly correlated with weight (r 0.44 P .004) and TRP inversely correlated with severity of reflux (r -0.32, P .04). Female sex was associated to nephrolithiasis (OR 17.0, P .02) and proteinuria (at T0 OR 5.8 P .03 at T1 OR 5.8, P .03). Daily proteinuria increased with age (r 0.66, P <.0001 at T0 and r 0.44 P .004 at T1) while protein-to-creatinine ratio decreased. Renal scars at T0 inversely correlated with glomerular and tubular function at T1 but they did not correlate with severity or laterality of reflux. CONCLUSION: Even if renal function remains stable through years, it is critical to identify the subjects with significant congenital renal damage.