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.