#1707447 X-linked Hypophosphatemia Treated With Anti-FGF23 Monoclonal Antibody

X-linked Hypophosphatemia (XLH) is a rare inherited disease characterized by low serum phosphate levels. In XLH, inactivating mutations in the phosphate regulating endopeptidase on the X chromosome gene (PHEX) leads to elevated serum fibroblast growth factor 23 (FGF23) levels that cause renal phosphorus wasting and subsequent hypophosphatemia. Most often diagnosed in childhood, XLH typically manifests as rickets, growth failure, and osteomalacia. We present a patient with recurrent low serum phosphorus diagnosed with XLH in adulthood and discuss the patient's clinical manifestations and treatment response to burosumab.