Osteomalacia

Question 1

What is osteomalacia?

Answer 1

Poor bone mineralisation leading to soft bone due to lack of vitamin D

Question 2

Give 3 symptoms of osteomlacia.

Answer 2

1. Bone pain and tenderness.
2. Fractures.
3. Wadding gait.

Question 3

An elderly lady with bone pain is found to have hypocalcaemia, hypophosphataemia and a raised ALP. What is the most likely diagnosis?

Answer 3

Osteomalacia.

Question 4

Why is osteomalacia less common in the UK than it once was?

Answer 4

Used to be common because we have little sunlight in the UK
Now foods are fortified with vitamin D.

Question 5

Give 3 risk factors for osteomalacia.

Answer 5

1. Lack of exposure to sunlight e.g. indoors, lots of clothing
2. Darker skin
3. Malabsorption disorders e.g. IBD
4. Low dietary vitamin D e.g. vegan
5. Kidney disease - CKD (they activate vitamin D)

Question 6

In the skin, ________ (made from ________) is metabolised to vit D3, in the presence of _______.

Answer 6

previt D3
cholesterol
UVB

Question 7

Vitamin D is important for bones because ________.

Answer 7

It is needed for the absorption of calcium and phosphate from the GI tract

Question 8

In the ________, vitamin D3 is metabolised to _________.

Answer 8

Liver
Calcidiol/25-hydroxyvitamin D

Question 9

In the _______, _________ is metabolised to __________ (calcitriol).

Answer 9

Kidney
25 hydroxyvitamin D
1,25-dihydroxyvitamin D

Question 10

How does the body respond to low vitamin D?

Answer 10

There will be low calcium and phosphate (because vitamin D is needed to absorb them).
So, PTH is released.
PTH mobilises calcium from bones
= bone weakness –> osteomalacia.

Question 11

What is Rickets?

Answer 11

Osteomalacia in children, before the growth plates have fused

Question 12

Give 4 signs + symptoms of osteomalacia.

Answer 12

1. Fatigue, bone pain (esp. hip/rib/pelvis/thigh/foot) and tenderness.
2. Dull ache that is worse on weight-bearing exercises
3. Fractures – esp NOF, abnormal fractures
4. Muscle weakness/aches - waddling gait, difficulty with stairs

Question 13

Give 4 signs + symptoms of Rickets.

Answer 13

1. Growth retardation, hypotonia
2. Knock knees, bowed legs
3. Widened epiphyses at the wrists
4. Hypocalcaemic tetany (intermittent muscular spasms) may occur in
   severe cases

Bow legs = varus
Knock knees = valgus

Question 14

Outline the investigations for osteomalacia.

Answer 14

1. Blood:
   * Low Ca2+ and phosphate
   * Raised serum alkaline phosphatase
   * Elevated parathyroid hormone
   * Low 25-hydroxy vitamin D
2. Biopsy:
   * Shows incomplete mineralisation
   * GOLD STANDARD TEST but not practical
3. X-ray:
   * Shows defective mineralisation
   * Looser’s pseudofractures/zones - low-density bands extending from the
   cortex inwards in the shafts of the long bones e.g femur and pelvis

Question 15

What is the first line investigation for osteomalacia?

Answer 15

Serum 25-hydroxy vitamin D

• Serum 25-hydroxyvitamin D ( less than 25 nmol/L is Vit D deficiency, 25-50 nmol/L is vit D insufficiency, greater than 75 nmol/L is optimal.

Question 16

What is the gold standard test for osteomalacia?

Answer 16

Iliac bone biopsy with double tetracycline labelling

Question 17

In osteomalacia, ALP will be ..

Answer 17

High

Question 18

What is the supplementary vitamin D (that you would give for osteomalacia) called?

Answer 18

Cholecalciferol