Metabolic bone disease

Question 1

Discuss your approach to metabolic bone disease causes

Answer 1

D/o of mineralisation
- vitamin D deficiency
D/o of matrix formation
- osteogenesis imperfecta
D/o of excessive/reduced bone absorption 
- hyperparathyroidism
- osteopetrosis

Question 2

What is the most common cause of rickets in infants?

Answer 2

Vitamin D deficiency

Question 3

What is the most common cause of rickets in older children?

Answer 3

Dietary calcium deficiency

Inherited hypophosphataemia

Question 4

What abnormalities can occur with the metabolism of vitamin D?

Answer 4

1. Nutritional
2. Impaired absorption
3. Impaired hydroxylation
4. Incr metabolism
5. Decr renal synthesis
6. End organ resistance

Question 5

Which substances cause poor calcium bioavailability?

Answer 5

Phytates

Oxalates

Question 6

Name risk factors for vitamin D deficiency

Answer 6

Lack of sunlight exposure
Incr skin pigementation
Prolonged breastfeeding
Prem
Mother vitamin D deficient
Vegetarian diet

Question 7

Name causes of impaired vitamin D absoprtion

Answer 7

Steatorrhoea
Biliary obstruction
Neonatal hepatitis

Question 8

Name causes of impaired vitamin D hydroxylation

Answer 8

Immature liver
Prem
Severe liver disease

Question 9

Name causes of increased vitamin D metabolism

Answer 9

Phenobarbitone

Question 10

Name causes of decreased renal synthesis of 1,25 dihydroxyvitamin D

Answer 10

Renal failure

Question 11

What abnormalities can occur with the metabolism of phosphate?

Answer 11

1. Nutritional
2. Impaired absorption
3. Renal loss

Question 12

Name causes of impaired phosphate intake

Answer 12

Prem (soya bean prep)

VLBW (BF not enough)

Question 13

Name causes of impaired intestinal phosphate absorption

Answer 13

Aluminum hydroxide

Question 14

Name causes of impaired renal loss of phosphate

Answer 14

1. Hypophosphataemia
2. Fanconi syndrome
3. Distal tubular acidosis
4. Tumour induced

Question 15

What genetic forms are there of hypophosphataemic rickets?

Answer 15

X linked
AD
AR

Question 16

Which gene is involved in X linked hypophosphataemic rickets

Answer 16

PHEX (inactivation)

Question 17

Which gene is involved in autosomal dominant hypophosphataemic rickets

Answer 17

FGF23 (activation)

Question 18

Which gene is involved in autosomal recessive hypophosphataemic rickets

Answer 18

DMP1 (inactivation)

ENPP1 (inactivation)

Question 19

What is Fanconi syndrome?

Answer 19

A syndrome of inadequate reabsorption in the proximal renal tubules of the kidney

Question 20

Name causes of Fanconi syndrome

Answer 20

Cystinosis
Lowe's syndrome
Tyrosinaemia
Galactosaemia
Hereditary fructose intolerance
Wilson's disease
Heavy metal toxicity
Idiopathic

Question 21

What do you need to consider in a child with FTT, acidosis and rickets?

Answer 21

Distal tubular acidosis

Question 22

Name clinical features of metabolic bone disease

Answer 22

Bony deformity
Short stature
Developmental delay
Hypotonia
Proximal mm weakness
Convulsions
Metabolic acidosis
Recurrent LRTIs

Question 23

Name bony deformities

Answer 23

Widening of long bone metaphysis
Bow legs
Genu varum
Harrison's sulcus
Rickety rosary
Craniotabes
Frontal/parietal bossing
Kyphoscoliosis

Question 24

Name radiological features of rickets

Answer 24

Delayed epiphyseal development
Growth plate widening
Splaying + cupping of metaphysis
Irregularity and fraying of metaphysis end
Osteopenic bones
Thin cortices
Trabecular patterns
Subperiosteal erosions

Question 25

Name causes of hypocalcemia biochemically

Answer 25

Actual decrease

Hypoalbuminaemia

Question 26

How do you treat nutritional vitamin D deficiency?

Answer 26

1000-5000IU/day 6w-3m

Question 27

How do you treat convulsions or apneic attacks in nutritional vitamin D deficiency?

Answer 27

Calcium gluconate 10% 1-2ml/kg as slow ivi infusion

Question 28

How do you treat impaired absorption vitamin D deficiency?

Answer 28

10000-50000IU/day

Question 29

How do you treat increased metabolism vitamin D deficiency?

Answer 29

100IU/day

Question 30

How do you treat decreased renal synthesis vitamin D deficiency?

Answer 30

25000-50000IU/day
OR
0.5ug/day 1.25OH D3

Question 31

Name an oral phosphate binding agent

Answer 31

Calcium carbonate

Question 32

What is the daily recommended dietary calcium intake?

Answer 32

800-1200mg/day

Question 33

How do you treat hypophosphataemic rickets?

Answer 33

1. Incr oral phosphate intake
   - Joulies solution: 1.5-3g phosphorus/24 hours in 4-5 divided doses
   OR
   - Phosphate enema 5-15ml q6h orally
2. Give calcium
   - 0.5ug 1.25OH D3 daily
3. Give treatment until late adolescence

Question 34

How do you treat distal renal tubular acidosis?

Answer 34

2-3mmol/kg/day Shohl’s solution

Question 35

How do you diagnose osteoporosis in children?

Answer 35

Presence of clinically significant fracture
history
1. 1 or > of the following
- 1 long bone fracture of lower extremities
- 1 vertebral compression fracture
- 2 or > long bone fractures of upper extremities
2. Low bone mass / mineral content
- DEXA BMD z score ≤ 2
- Adjusted for age, sex & body size

Question 36

Name causes of osteoporosis

Answer 36

1. Decr bone matrix formation
   - osteogensis imperfecta
   - corticosteroid excess
   - PEM
   - vitamin C deficiency
   - copper deficiency
2. Incr bone resorption
   - immbolisation
   - marrow hyperplasia
   - juvenile idiopathic osteoporosis
   - hyperparathyroidism