X-Linked Hypophosphatemia. Case Report.

Introduction X-linked hypophosphatemia is a rare, heritable disorder. The resultant chronic hypophosphatemia leads to progressive deterioration in musculoskeletal function, including impaired growth, rickets, and limb deformities in children. Case Presentation A 16-year-old girl was born with congenital dislocation of the right hip joint. However, following the onset of walking, recurrent lower limb dislocations were noted. Laboratory investigations revealed ALP - 1383.9 U/L and P - 0.90 mmol/L. The patient was diagnosed with hypophosphatemic rickets at 1.5–2 years old. Treatment included alfacalcidol and phosphorus supplementation. From childhood, she reported persistent leg pain, exacerbated by physical activity, and short stature. Cytogenetic analysis: a normal 46, XX karyotype. Genetic testing identified a pathogenic variant in the PHEX gene, NM_000444.6(PHEX):c.[1080-2A>G];[1080-2=], confirming the diagnosis of X-linked hypophosphatemia. Recently laboratory results showed ALP of 136 U/L and P of 0.62 mmol/L. She is currently on alfacalcidol and phosphate supplementation. Subsequent laboratory and radiological assessments revealed a parathyroid adenoma, which was surgically excised. Ongoing management and monitoring remain essential. Discussion X-linked hypophosphatemia (XLH) is a rare, lifelong disorder caused by increased circulating levels of FGF23, that leads to consequent abnormal bone mineralization (1). The worldwide prevalence is approximately 1/47 000. The disease affects both sexes equally. It is caused by various variants in the PHEX gene. Although the mechanism is unknown (2). The most common presentation is leg deformities in childhood. Progressive bowing, torsion rotation of tibiae, and short stature represent the predominant skeletal outcomes, which do not entirely resolve (3). There are currently two treatment options: active vitamin D analog, phosphate supplementation and the monoclonal antiFGF23 antibody burosumab (4). Overall, the lifetime burden of illness is high in XLH, complicated often by a lack of understanding of the disease and its management by both patients and clinical providers (5). Conclusions This case underscores the importance of early intervention, lifelong multidisciplinary care, and the potential benefits of emerging therapies to optimize patient outcomes and quality of life (4).