Vitamin-D Resistant Rickets

Vit-D Resistant Rickets (Hypophosphatemic Rickets)/(Familial hypophosphatemia) –         Non-nutritional –         Most frequent cause of dwarfism –         Fails to respond to usual dose of Vit-D but responds to massive dose of Vit-D –         X-linked dominant (most common), Autosomal recessive & Sporadic PATHOLOGY: a)     Defect in proximal tubular reabsorption of phosphate; b)    Defect in conversion of 25(OH)D3 → 1,25(OH)D3. C/F: –         Short stature –         Pain –         Deformity– bow leg, knock-knee, Tackle deformity(Wind-swept deformity) –         Marked ligamentous instability –         Waddling gait- due to Coxa vara –         Usual findings of rickets Lab Findings:

  • S. Calcium level- ↓/N
  • S. Phophate̶  ↓↓
  • S. ALP- ↑↑↑
  • S. PTH level- N
  • Urine- Phosphate ↑↑↑
  • No Amino acid/Glucose/Bicarbonate /Potassium in urine (differentiating features from Renal Rickets due to Fanconi syndrome)

Treatment: 1)    Phosphate supplementation (1-2 gm/day): Joulie’s solution 5-10 ml 4times a day (30.4 mg of phosphorus/ml); diet rich in phosphorus 2)    Large dose of Vitamin-D: 50,000 to 500,000 IU/day; Toxic side effects- Hypercalcemia, Renal injury 3)    Titration of dose by- a)Urine Sulkowitch Test: +1 or +2 maximum; b)S. Ca-level ≤ 12mg/dL; c)Urine excretion of Ca ˃200mg/day 4)    Vit-D supplementation:  until growth complete, after that →may be continued to prevent osteomalacia. 5)    Correction of deformities: A)SPLINTS– to prevent progression; B)SURGERY– after closure of epiphyses; – when X-ray shows healed stage of Rickets.