Osteomalacia

Question 1

What is it?

Answer 1

Defective bone mineralisation causing soft bones

Normally caused by VitD deficiency in adults

Known as rickets in children and can lead to bone deformity

Question 2

What is the pathophysiology?

Answer 2

VitD is created from cholesterol due to UV exposure

VitD is important for calcium and phosphate absorption and regulates bone turnover

Low levels of VitD leads to low calcium and phosphate which leads to defective bone mineralisation

Low calcium causes hyperparathyroidism which increases bone resorption

Question 3

What are the symptoms?

Answer 3

Fatigue
Bone pain
Muscle weakness- waddling gait/difficulty climbing stairs
Muscle aches
Pathological or abnormal fractures
Bone fragility
Looser zones- fragility fractures that go partially through bone

Question 4

What are the risk factors?

Answer 4

Inadequate VitD intake
Renal disease
Liver disease
Drugs
Darker skin
Poor sunlight exposure
Colder climates

Question 5

What investigations are needed?

Answer 5

Bloods

• U&Es- renal abnormalities
• LFTs- raised ALP suggests increased osteoblast activity
• Calcium- usually normal due to secondary hyperPTH
• Phosphate- low
• PTH- high
• Serum 25 hydroxyvitamin D
• -<25nmol/L= Def
• • 25-50= insuf
• -75= optimal

XR

• shows looser zones of defective mineralisation
• children= widening of epiphyseal plates

Question 6

What is the management?

Answer 6

Supplementary VitD

• 50,000 IU once weekly for 6 wks
• 20,000 IU twice weekly for 7wks
• 4000 IU daily for 10 wks

Then maintenance dose of 800IU/ day minimum

If insuf levels then start on maintenance dose