X-linked hypophosphatemia: Management and treatment prospects.

X-linked hypophosphatemia (XLH), due to a PHEX gene mutation, is the most common genetic form of rickets and osteomalacia. Manifestations in children consist of rickets, lower-limb bone deformities, bone pain, failure to thrive, dental abscesses, and/or craniostenosis. Adults may present with persistent bone pain, early osteoarthritis, hairline fractures and Looser zones, enthesopathy, and/or periodontitis. Regardless of whether the patient is an infant, child, adolescent or adult, an early diagnosis followed by optimal treatment is crucial to control the clinical manifestations, prevent complications, and improve quality of life. Treatment options include active vitamin D analogs and phosphate supplementation to correct the 1.25(OH)2 vitamin D deficiency and to compensate for the renal phosphate wasting, respectively. The recently introduced FGF23 antagonist burosumab is designed to restore renal phosphate reabsorption by the proximal tubule and to stimulate endogenous calcitriol production. In Europe, burosumab is licensed for use in pediatric patients older than 1 year who have XLH. This review discusses the diagnosis and treatment of XLH and describes the indications of the various available treatments.