Osteomalacia

Question 1

What is osteomalacia?

Answer 1

Vitamin D deficiency causing defective bone mineralisation

Leads to weak bones, bone pain, muscle weakness and fractures

Called rickets if it occurs in children prior to their growth plates closing

Question 2

What is the pathophysiology of osteomalacia?

Answer 2

1. Vitamin D is essential for the absorption of calcium and phosphate from intestines/kidneys/bone
2. So deficiency leads to low serum calcium and phosphate
3. Calcium and phosphate are needed for construction of bone, so low levels cause problems with bone mineralisation
4. Low calcium causes PTH secretion and PTH works to increase reabsorption of calcium from the bones, causing further problems with bone mineralisation.

Question 3

How does osteomalacia present?

Answer 3

May be asymptomatic

Fatigue
Bone pain

Muscle weakness - proximal myopathy

Myalgia
Pathological fractures

Question 4

Risk factors for osteomalacia

Answer 4

Darker skin
Low exposure to sunlight
Colder climates

Question 5

Investigations in osteomalacia

Answer 5

Serum 25-hydroxyvitamin D:

• <25nmol/L - vitamin D deficiency
• 25-50 - vitamin D insufficiency
• 75 or higher is optimal

Calcium - low
Phosphate - low

LFTs - ALP may be high

PTH - may be high

X-rays –> may show osteopenia

DEXA scan - low bone mineral density

Question 6

Treatment of osteomalacia

Answer 6

Supplementing vitamin D - loading dose first usually

Plus calcium supplementation if dietary calcium is low