Bilateral Genu Valgum in Children

Primary Pathologic Causes

X-linked hypophosphatemia (XLH) causes severe leg bowing, characterized by renal phosphate wasting, elevated FGF23 levels, hypophosphatemia, and elevated alkaline phosphatase, according to the American Academy of Pediatrics 1
Clinical features of XLH include abnormal gait, lower limb deformity, decreased growth velocity, and disproportionate short stature, as reported by the American College of Medical Genetics and Genomics 1
Radiographs of XLH show partial fraying and irregularity of the distal femoral and proximal tibial growth plates, as described by the Pediatric Orthopedic Society of North America 2
Biochemical screening for XLH should include serum phosphate, alkaline phosphatase, vitamin D levels, parathyroid hormone, and FGF23, as recommended by the Endocrine Society 2
Genetic testing for PHEX gene mutations confirms diagnosis of XLH in 70-90% of cases, according to the National Institute of Child Health and Human Development 1, 2

Glycogen storage disease type III can present with genu valgus as part of musculoskeletal manifestations, characterized by hepatomegaly, hypoglycemia, hyperlipidemia, and myopathy, as reported by the American College of Medical Genetics and Genomics 3

Untreated pathologic genu valgum leads to abnormal gait, decreased mobility, progressive joint damage, and early osteoarthritis, as warned by the American Academy of Orthopaedic Surgeons 2, 4
In XLH, specific treatments (phosphate supplementation and active vitamin D) can improve bowing, making early diagnosis critical, according to the Kidney Disease: Improving Global Outcomes (KDIGO) foundation 2