• Skeletal abnormalities due to chronic renal failure

• Kidneys are vital of vit D metabolism, and phosphate secretion – when disturbed results in:
  • Osteomalacia (or rickets)
  • Secondary hyperparathyroidism
  • Metastatic calcification
  • Osteoporosis

Rickets:

Deficiency of vitamin D during bone development (infancy)

• Essential for absorption and metabolism of calcium and phosphate
• Deficiency leads to:
  • Defect in bone matrix mineralization and skeletal development
  • Defective absorption of calcium and phosphate
  • Chronic renal disease: renal rickets

Etiology:

• 1. Vitamin D deficiency
  • Reduced endogenous synthesis due to lack of exposure to the sun
  • Dietary deficiency (fish, eggs, butter, milk)
  • Malabsorption and metabolism failures due to liver disease, pancreatic insufficiency, kidney
• 2. Abnormal metabolism of vitamin D:
  • Chronic renal failure
  • Vitamin D resistant rickets
  • Anticonvulsant osteopathy
• 3. Phosphate depletion: antacids contain al(oh)3 which bind phosphate, excess renal secretion of po4
  • Fanconi syndrome
  • X linked hypophosphatemic rickets
• 4. Renal tubular acidosis

Physiology:

• Vit D is essential for intestinal absorption of Ca++ and po4
• Co-factor in mobilization of Ca++ from bone
• Stimulates PTH dependent re-absorption of Ca++ by the distal renal tubules

Clinical:

• Craniotabes – unossified areas of cranium
• Rachitic rosary – overgrowth of costochondral cartilage
• Pigeon chest deformity
• Lordosis
• Knock knees/ bow legs
• Enlarged epiphyses
• Osteomalacia
• Hypocalcaemic tetany
• Dental:
  • Multiple spontaneous periapical abscess in 1ry & 2ry dentition
  • Enlarged pulp chambers
  • Thin easily abraded enamel
  • Marked interglobular dentine

Histology: ↑ Osteoid matrix in bones

Lab:

• Normal or ↓ ca++
• ↓ po4
• ↓ vit D metabolites
• ↑ alkaline phosphatase

Management: Replacement therapy

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