X-Linked Hypophosphatemic Rickets: A Pediatric Case Report

Abstract

X-linked hypophosphatemic rickets is a monogenic disease, characterized by hyperphosphaturia and hypophosphatemia. Due to its rarity and wide phenotypic variability, a diagnostic delay is common in X-linked hypophosphatemic rickets. Short stature, limb deformities, dental anomalies, craniosynostosis and chronic pain are common in this disease. Recently, burosumab, a monoclonal antibody anti-fibroblast growth factor 23, was approved for the treatment of X-linked hypophosphatemic rickets. Awareness among clinicians must be increased to improve the care of these patients. We present a clinical case of a 4-year-old girl presented with deformities of the lower limbs and an abnormal gait, associated with hyperphosphaturia and hypophosphatemia. Asymptomatic Arnold Chiari malformation was identified. No dental problems were detected. The diagnosis of X-linked hypophosphatemic rickets was confirmed by the identification of a PHEX mutation. The patient developed diarrhea, nephrocalcinosis, and hyperparathyroidism secondary to conventional therapy with phosphate supplements. Burosumab was initiated with a fast increase on serum phosphate levels and a decrease on alkaline phosphatase. With the description of this case, we highlight the clinical manifestations and complications of X-linked hypophosphatemic rickets and its treatment and we discuss new treatment strategies to improve the quality of life of these patients.

Keywords

• antibodies
• monoclonal
• humanized/therapeutic use
• burosumab
• child
• familial hypophosphatemic rickets/drug therapy