Articular Manifestations of X-Linked Hypophosphatemic Rickets in Saudi Children: A Retrospective Cohort Study

Abstract

Introduction: This retrospective cohort study aimed to describe the articular manifestations in Saudi children with X-linked hypophosphatemic rickets (XLHR). Materials and Methods: The medical records of children with XLHR were retrospectively reviewed. The diagnosis of XLHR was confirmed biochemically by low serum phosphorus and elevated alkaline phosphatase, radiologically by the evidence of active rickets and genetically by phosphate-regulating gene with homology to endopeptidases (PHEX) gene mutations. Results: Twenty-two patients with XLHR (10.8 years + 4.9) were enrolled. All children were followed at King Faisal Specialist Hospital & Research Center for a mean duration of 8.7 years (+3.7). Clinically, all patients had disproportionate short stature (-2.5 standard deviation +1.3) with varying degrees of skeletal deformities, including genu varum in 68%, genu valgum in 18%, coxa vara in 14%, bowing of tabia in 32%, and history of fractures in 32% of children. Hearing impairment was noted in two children. Biochemically, all patients showed increased urinary phosphate loss with hypophosphatemia 0.67 mmol/l (+0.15) and elevated serum alkaline phosphatase levels 522 IU/l (+133). Genetically, hemizygous PHEX mutation (C746F) was reported in seven patients. Radiologically, four children had osteoarthritis and three had enthesopathies. Four patients craniosynostosis. All children were on oral inorganic phosphate salts (50–70 mg/kg/day), combined with 1,25(OH)2D3 (alfacalcidol or calcitriol, 30–40 ng/kg/day). Conclusion: Patients with XLHR frequently present with varying degrees of joint deformities that are not completely resolved with either medical or surgical treatment. Long-term skeletal complications of XLHR that present in adults are less common in children and adolescents.