Musculoskeletal System >
Osteomalacia & Rickets

“Normal bone tissue but with abnormal or impaired bone mineralisation resulting in soft bones

  • Rickets: during growth in children
  • Osteomalacia: After epiphysis fusion (adults)
Risk Factors
  • Poor diet
  • Lack of sunlight e.g. northern hemispheres, darker skin (Asian, Afro-Caribbean, Middle Eastern origin), homebound elderly populations
  • Prematurity
  • Exclusive breastfeeding (especially for > 6 months)
  • Medication – phenytoin or other anticonvulsants
Epidemiology
  • Common in the past but fortified foods in 20th century have reduced its incidence.
  • However, there is a small increase in cases of rickets in UK due to vit D deficiency in a significant number of population
  • More common in people with darker skin as they require more sunlight for adequate vitamin D
Aetiology
  • Vitamin D, calcium deficiency – most common cause
    • Lack of sunlight
    • Poor dietary intake e.g. low-fat diet, lack of dairy products (vegan diet)
    • Malabsorption e.g. coeliac disease, Crohn’s disease
  • Drug-induced e.g. anticonvulsants – use liver and kidney hydroxylase enzymes that convert Vit D for its own metabolism
  • Inherited genetic defect – e.g. congenital deficiency of 1 alpha-hydroxylase (promotes the conversion of active Vit D)
  • Liver disease e.g. cirrhosis
    • Liver unable to convert inactive vitamin D to 25 hydroxyvitamin D
  • Renal failure – kidneys can’t convert 25 hydroxyvitamin D to calcitriol
Clinical Presentation
  • Osteomalacia and rickets:
    • Diffuse bone and joint pain
    • Muscle tenderness
    • Proximal myopathy
    • Increased fracture risk with minimal trauma
    • Hypocalcaemia
      • Muscle cramps, twitching, tingling in hands and feet, seizures
  • Rickets:
    • Bone pain
    • Soft, weakened bone resulting in skeletal deformities
      • Bowed legs (genu varum)
      • Knock knees
      • Thickening of ankles, wrists and knees
      • Soft skull bones (craniotabes)
      • Delayed closure of fontanelles
      • Prominent frontal bone
      • Scoliosis (rarely)
    • Poor bone growth and development
      • Shorter height than average
    • Protruding abdomen (severe disease)
Pathophysiology
  • Calcitriol (vit D3) = hormonally active form of vit D
    • Function:
      • Promote dietary calcium absorption to maintain calcium levels
      • Increases renal tubular calcium reabsorption
      • Increase calcium deposition into bones
      • Promote bone mineralisation, strengthening and formation (after normalisation of Calcium levels)
  • Lack of vitamin D → lack of calcitriol → reduced calcium → impaired bone mineralisation (osteoblasts unable to deposit calcium or phosphate into the inorganic matrix)
Investigations
  • Blood tests
    • Low 25-hydroxy vitamin D
    • Raised alkaline phosphatase
    • Low calcium and phosphate
    • High PTH
  • X-ray
    • Adults – translucent bands, pseudofractures (looser zones) often in superior and inferior pubic rami
    • Children Metaphyseal cupping and flaring, bowed legs
Management
  • Improve dietary intake of Vit D and calcium
  • Oral calcium and vit D supplementation or yearly vit D injections
    • Vit D injections mainly necessary if oral intake is not possible or patient has intestinal or liver disease
  • Adequate sun exposure
  • Treating underlying cause
  • Vit D supplementation:
    • Pregnant and breastfeeding women
      • 10mcg of Vit D daily between Oct-March (when days are shorter)
    • Babies from birth to 1 year old (regardless of feeding status)
      • 8.5-10mcg daily supplement
      • Those on formula do not need Vit D as it is fortified unless they are drinking < 500ml a day of formula
    • Children between 1-4 years old
      • 10mcg daily
Complications
  • Skeletal Deformities

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