Rickets and Osteomalacia
(Etiology, Pathogenesis, Clinical Manifestations )
Definition
Both are due to impaired bone mineralization, most often caused by vitamin D deficiency or phosphate metabolism disorders.
Pathogenesis
- Vitamin D deficiency or phosphate loss → ↓ calcium and phosphate absorption from the intestine.
- Leads to hypocalcemia, which triggers parathyroid hormone (PTH) release.
- PTH increases bone resorption and reduces renal phosphate reabsorption → hypophosphatemia.
- Result: defective mineralization of osteoid → accumulation of unmineralized bone matrix.
- In children, this affects growing bones → deformities (rickets).
In adults, leads to soft, weak bones and fractures (osteomalacia).
Clinical Manifestations
- Rickets (in children)
- Skeletal deformities:
- Bowed legs (genu varum).
- Knock-knees (genu valgum).
- Frontal bossing (prominent forehead).
- Rachitic rosary (enlarged costochondral junctions).
- Harrison's groove (depression along the rib cage).
- Delayed milestones (e.g., sitting, walking).
- Growth retardation.
- Hypotonia, muscle weakness.
- Dental problems (delayed tooth eruption, enamel defects).
- Seizures (from hypocalcemia, in severe cases).
- Osteomalacia (in adults)
- Bone pain (especially in hips, lower back).
- Muscle weakness (especially proximal muscles).
- Waddling gait.
- Fractures (esp. ribs, vertebrae, femoral neck).
- Low serum calcium, phosphate, ↑ alkaline phosphatase.