Metabolic Bone Disease Diagnosis

Diagnostic Approach

The National Kidney Foundation recommends measuring calcium, phosphorus, creatinine, alkaline phosphatase, parathyroid hormone, and 25(OH) vitamin D levels in serum 1, 3
Calculate TmP/GFR (maximum rate of renal tubular reabsorption of phosphorus per GFR) to evaluate renal phosphorus loss 1, 3
Measure 1,25(OH)₂ vitamin D and intact FGF23 in cases with a negative family history 1, 3

Conventional skull radiography has no place in the diagnosis of modern metabolic bone diseases 5
Prefer MRI of the skull (with black bone sequence when available) for accurate evaluation of bone structure and exclusion of craniosynostosis 3, 2
Perform renal ultrasound to check for nephrocalcinosis, especially in patients with hypercalciuria 1, 3

In X-linked hypophosphatemia (XLH), conventional treatment includes oral phosphate supplements always in combination with active vitamin D, with doses of 20-60 mg/kg body weight daily based on elemental phosphorus 1
Early treatment is associated with better outcomes, with a goal of healing rickets as documented by normalization of alkaline phosphatase and radiological improvement 1

The American College of Rheumatology notes that Paget's disease can present with a mixed osteolytic and osteosclerotic image in the skull, with elevated alkaline phosphatase and characteristic age of onset >50 years 4
Hypophosphatasia presents with generalized bone pain and muscle weakness, with low alkaline phosphatase levels and mixed lytic and sclerotic lesions 4
Osteomalacia is generally characterized by low serum phosphorus, elevated alkaline phosphatase, low 25-hydroxy-vitamin D, elevated parathyroid hormone, and osteoid accumulation on imaging 4