Osteomalacia

Question 1

What is osteomalacia?

Answer 1

The softening of the bones is generally secondary to vitamin D deficiencies leading to incomplete mineralisation of the bone

Question 2

What is rickets?

Answer 2

In growing children, rickets is characterised by defective mineralisation of the growth plate cartilage leading to skeletal deformities and reduction of growth secondary to vitamin D deficiency and subsequent incomplete bone mineralisation

Question 3

What is the epidemiology?

Answer 3

Vitamin D deficiency is common in both children and adults
The peak incidence of osteomalacia is 50-60 years
Males and females are equally affected

Question 4

What are the risk factors for osteomalacia?

Answer 4

Dark skin, especially in South Asian, African-Caribbean, and Middle-Eastern people
Vitamin D deficiency is as high as 94% in otherwise healthy South Asian adults
Family history of vitamin D deficiency
Age >65
Pregnancy
Obesity
Covering of the face and body
Housebound/institutionalised patients
Poverty
Vegetarianism
Alcoholism
Living in a high altitude

Question 5

Which organ produces vitamin D?

Answer 5

the skin (in response to UV radiation)

Question 6

What molecule does the skin use to produce vitamin D?

Answer 6

cholesterol

Question 7

What organ converts vitamin D into its active form?

Answer 7

kidneys

Question 8

Why does chronic kidney disease increase risk of vitamin D deficiency?

Answer 8

the kidneys activate vitamin D into its active form

Question 9

Give a GI risk factor for vitamin D deficiency:

Answer 9

malabsorption disorders e.g. IBD (not enough vitamin D is absorbed)

Question 10

What is the role of vitamin D in bone mineralisation? (2)

Answer 10

1) vitamin D is essential for calcium and phosphate absorption in the intestines, reabsorption in the kidneys and for regulating bone turning over (promoting bone reabsorption to increase serum calcium)

2) calcium and phosphate are required for bone construction

Question 11

Describe how a secondary hyperparathyroidism can impair bone mineralisation?

Answer 11

the low serum calcium as a result of low vitamin D increase parathyroid hormone which promotes calcium reabsorption from the bones

Question 12

Give 6 presentations associated with osteomalacia:

Answer 12

1) fatigue
2) bone pain
3) muscle weakness
4) muscle aches
5) pathological/ abnormal fractures
6) looser zones

Question 13

What are ‘looser zones’?

Answer 13

Fragility fractures that go partially through bone

Question 14

What are the signs of osteomalacia on examination?

Answer 14

1. Proximal muscle weakness
2. Muscle wasting associated with proximal muscle weakness
3. Waddling gait if the bone pain/ proximal muscle weakness is severe

Question 15

What are 2 differential diagnoses for osteomalacia?

Answer 15

1. Osteoporosis
2. Paget’s disease of the bone

Question 16

What is the difference between osteoporosis and osteomalacia?

Answer 16

Asymptomatic until a fragility fracture develops
Osteomalacia is painful at the onset
Osteomalacia has a history of limited sunlight exposure etc.
Osteoporosis: normal serum calcium, phosphate, ALP, vitamin D, and PTH
Osteomalacia: increased ALP, low phosphate, low vitamin D, increased PTH due to secondary hyperparathyroidism

Question 17

What is the difference between Paget’s disease of the bone and osteomalacia?

Answer 17

Most patients are asymptomatic
Paget’s disease of the bone: only ALP raised
Osteomalacia: increased ALP, low phosphate, low vitamin D, increased PTH due to secondary hyperparathyroidism

Question 18

What is the lab test for vitamin D known as?

Answer 18

serum 25-hydroxyvitamin D

Question 19

What is the vitamin D threshold for vitamin D deficiency?

Answer 19

less than 25 nmol/L

Question 20

What range of vitamin D is considered vitamin D insufficiency?

Answer 20

25-50 nmol/L

Question 21

Will serum calcium be raised or low in osteomalacia?

Answer 21

low

Question 22

Will serum phosphate be raised or low in osteomalacia?

Answer 22

low

Question 23

Will alkaline phosphatase be raised or low in osteomalacia?

Answer 23

high

Question 24

Will parathyroid hormone be raised or low in osteomalacia?

Answer 24

high

Question 25

Give 2 imaging modalities indicated in osteomalacia:

Answer 25

1) DEXA scan
2) X-ray

Question 26

What is the first line medication for osteomalacia?

Answer 26

colecalciferol

Question 27

What is colecalciferol?

Answer 27

vitamin D3 supplement

Question 28

What is the standard maintenance dose for colecalciferol in osteomalacia/ vitamin D deficiency?

Answer 28

800-2000 IU per day

Question 29

What is often given alongside vitamin D?

Answer 29

Calcium supplementation

Question 30

How are osteomalacia patients monitored?

Answer 30

Check the patient’s 25-hydroxyvitamin D levels 2-3 months after starting therapy
If undergoing long-term treatment, patients should have annual monitoring for signs and symptoms of osteomalacia or over-treatment with vitamin D
Patients taking calcitriol should be assessed every 3 months along with a baseline renal ultrasound to evaluate for nephrocalcinosis or nephrolithiasis.

Question 31

What are 2 complications of osteomalacia?

Answer 31

1.Secondary hyperparathyroidism
2. Insufficiency fractures or pseudofractures