Delayed Diagnosis of Probable X-Linked Hypophosphatemia Revealed by a Femoral Fragility Fracture in a 33-Year-Old Man: A Case Report

We report the case of a 33-year-old man with short stature, lower limb deformities, and dental abnormalities since childhood, who had never received a diagnosis or specialized medical follow-up.He had sustained a femoral fracture after minor trauma at the age of 14.His mother and one of his sisters had a similar morphological appearance.He was admitted for mechanical pain in the right hip, which revealed a femoral fragility fracture.Clinical examination showed marked genu varum, bilateral tibial bowing, and multiple tooth loss.Laboratory investigations revealed severe hypophosphatemia with inappropriately preserved phosphaturia, indicating renal phosphate wasting, along with an elevated intact fibroblast growth factor 23 (FGF23) level, normal serum calcium and renal function, and elevated alkaline phosphatase.Based on these clinical, biochemical, and radiological findings, a diagnosis of probable X-linked hypophosphatemia (XLH) was made; PHEX gene sequencing could not be performed for financial reasons.After correction of 25hydroxyvitamin D insufficiency, treatment with divided doses of oral phosphate and active vitamin D was initiated; however, follow-up was limited by poor treatment adherence and financial constraints.This case suggests that XLH can remain undiagnosed until adulthood and that, in adults with short stature, lower limb deformities, low-trauma fractures, and dental abnormalities, serum phosphate should be measured.