Biochemical Disorders of Bone

Question 1

What is the most significant difference in investigation findings between osteoporosis and osteomalacia?

Answer 1

Osteoporosis - normal calcium and phosphate levels

Osteomalacia - low calcium and phosphate levels

Question 2

What condition presents with Looser’s Zones (psuedofractures) on XR?

Answer 2

Osteomalacia

Question 3

What is osteomalacia known as when it presents in children?

What is the most notable presentation of this condition?

Answer 3

Rickett’s

Bow shaped legs

Question 4

What causes osteomalacia?

Answer 4

Abnormal softening of bone due to insufficient mineralisation of osteoid - secondary to low levels of calcium and phosphate

Poor calcium levels - can be due to low levels of vit D = poor absorption

Question 5

What is osteoporosis?

What defines it?

Answer 5

Decreased bone density and increased pores

Bone density of less than 2.5 standard deviations below the mean

Question 6

What are the 2 types of osteoporosis?

Answer 6

Type 1 = post-menopausal (oestrogen is protective against osteoporosis)

Type 2 = old age

Question 7

What condition is sustained corticosteroid use associated with?

Answer 7

Osteoporosis

Question 8

What is first line treatment for osteoporosis?

What is their MoA?

What is their common side effect?

Answer 8

Bisphosphates - alendronate

Reduce osteoclast activity

Reflux and oesophageal erosions

Question 9

How is osteoporosis diagnosed?

Answer 9

DEXA bone scan

Question 10

What condition can cause hypercalcaemia as a result of increased bone breakdown leading to bone pain?

Answer 10

Hyperparathyroidism - increased levels of PTH (parathyroid hormone)

Question 11

What is Paget’s disease?

What causes the bone to be weak?

Answer 11

An abnormality in bone turnover

-> sclerotic weakened bone due to mosaic pattern of rebuilding bone (more porous and less stable structure)

Question 12

Paget’s disease is most commonly asymptomatic but when it does present how may it appear?

Answer 12

Thickened bone in axial skeleton (larger hats)

Warm skin to touch (increased metabolism of bone)

Question 13

What is osteopenia?

Answer 13

An intermediate stage before osteoporosis

1-2.5 standard deviations below the mean

Question 14

What bones are most likely to be affected by Paget’s disease?

Answer 14

• Skull
• Spine
• Pelvis

Question 15

What biochemistry would be different in Paget’s disease?

Answer 15

Raised ALP

Question 16

How is Paget’s disease managed (be specific with drug names)?

Answer 16

Bisphosphonates (if raised ALP) - PAMIDRONATE/ALIDRONATE

NSAIDS/other analgesias

Question 17

Long term use of corticosteroids is a strong risk factor for osteoporosis. If they were to fracture a bone what would be seen on XR?

Answer 17

Exuberant callus formation

corticosteroid induced osteoporosis

Question 18

What is the common side effect of biphosphates?

Answer 18

Oesphagitis - similar process of taking them to doxycycline

Can also cause osteonecrosis of the jaw - much rarer though

Question 19

A reduction in bone marrow density on Xray is seen in what condition?

Answer 19

Osteoporosis

Question 20

What is the name for the rare condition in which there is a defect in osteoclast function.
What does this result in?

Answer 20

Osteopetrosis

Hard and dense bone which is prone to fracture