chapter 21 - metabolic bone disease Flashcards

1
Q

name the 3 main groups of metabilic bone disease

A

osteoporosis
osteomalacia
osteitis fibrosa

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2
Q

define osteoperosis

A

abnormal decrease in bone mass per unit volume

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3
Q

mechanism of osteoperosis

A

low bone mass –> subsequent resorption –> increased bone fragility + increased tendency to fracture

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4
Q

what is the cause of primary osteoporosis

A

post menopausal osteoporosis

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5
Q

rate of bone loss post menopause relative to before?

A

pre: 0.3% per year
post: 3% per year

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6
Q

how does menopause affect the bones?

A

decreased estrogen - therefore increased osteoclastic activity

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7
Q

risk factors for primary osteoporosis - 6

A
caucasian
hereditary
premature menopause
early hysterectomy
smoking
alcohol abuse
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8
Q

clinical features of primary osteoporosis -3

A

back pain
thoracic kyphosis
fracture of distal radius - often initial event

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9
Q

3 investigations for the diagnosis of osteoporosis

A

xray
dexa scan
bone turn over and biochemical tests - usually normal

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10
Q

xray features of osteoporosis

A

wedging of vertebral bodies
end plate collapse
loss of normal trabecular pattern of bone

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11
Q

treatment of osteoporosis

A
  1. prevention: normal diet + atleast 1500mg ca per day from 20 yrs of age
  2. avoid RF
  3. HRT
  4. calcitonin or bisphosphonates if HRT CI
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12
Q

most effective therapy for osteoporosis

A

HRT

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13
Q

why must you monitor patients on HRTs ?

A

slightly increased risk of breast and uterine cancer

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14
Q

what is senile osteoporosis?

A

15 yrs after menopause and at the same age in men there is still a 0.5% decline in bone mass per year –> may lead to increased fractures from minor trauma

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15
Q

RF for senile osteoporosis

A
prolonged menopausal bone loss
chronic illness
urinary insufficiency
muscular atrophy
dietary deficiency
lack of exposure to sunlight
increased tendency to fall
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16
Q

typical fracture found in patients with senile osteoporosis

A

fracture of femoral neck of minor trauma

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17
Q

treatment of senile osteoporosis

A
  1. manage fracture
  2. optimise medical condition
  3. sodium fluoride + vitamin D may increase bone mass
  4. bisphosphonates may minimise further loss
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18
Q

causes of secondary osteoporosis - 6 broad groups

A
nutritional 
endocrine
drug
malignant disease
non malignant disease
other
19
Q

nutritional causes of secondary osteoporosis 3

A

scurrvy
malnutrition
malabsorption

20
Q

4 endocrine causes of secondary osteoporosis

A

hyperparathyroidism
gonadal insufficiency
cushings disease
thyrotoxicosis

21
Q

4 drug induced causes of 2 osteoporosis

A

corticosteroids
alcohol
nicotine
heparin

22
Q

3 malignant diseases causing secondary osteoporosis

A

carcinomatosis
leukemia
multiple myeloma

23
Q

4 non malignant diseases causing secondary osteoporrosis

A

rheumatoid arthritis
ankylosing spondylitis
tuberculosis
chronic renal disease

24
Q

other causes of secondary osteoporosis 2

A

weightlessness - space workers

immobilisation

25
what is the mechanism of rickets and osteomalacia?
inadequate mineralisation of bone
26
which population presents with rickets ?
children
27
which population presents with osteomalacia?
adults
28
which areas are affected in rickets
areas of endochondral growth
29
which areas are affected in osteomalacia?
areas of new bone in the skeleton is incompletely calcified and structurally weak
30
3 reasons for inadequate bone mineralisation
1. calcium deficiency 2. hypophosphataemia 3. aberrant metabolic pathway for vitamin D
31
5 causes of aberrant metabolic pathway for vitamin D
1. nutritional 2. lack of sunlight 3. intestinal malabsorption 4. decreased 25 hydroxylation - liver disease/ anticonvulsants 5. reduced 1 alpha hydroxylation - renal disease
32
8 clinical features of rickets
1 failure to thrive 2 tetany, convulsions 3 muscular flaccidity 4 deformity of skull - craniotabes 5 thickening of ankles knees and wrists from epiphyseal overgrowth 6 enlargement of costachondral junctions - rickety rosary 7 lateral indentation of chest - harrisons sulcus 8 bow legs, coxa vara, spinal deformtiy, fractures of long bones
33
what is craniotabes?
skull deformity in rickets
34
what is rickety rosary
enlargement of costachondral junctions
35
what is harrisons sulcus
lateral indentation of chest
36
4 clinical features of osteomalacia
more insidious than rickets bone pain weight loss stress or insufficiency fracture
37
radiological features of rickets 2
thickening and widening of the growth plate | bowing of the diaphysis
38
radiological features of osteomalacia 3
looser zone biconcave vertebrae trefoil pelvis
39
what is the loosers zone?
a transverse band of rarefaction in an otherwise normal bone - osteomalacia
40
what is trefoil pelvis?
lateral indentations into the pelvis by the acetabulae - osteomalacia
41
biochemistry of rickets and osteomalacia
- decreased serum calcium and phosphate - increased alkaline phosphatase - diminished urinary excretion of calcium - in vitamin D deficiency 25 HCC levels are low - diminished calcium phosphate product ( < 2.4mmol/l)
42
which value of calcium phosphate product is diagnostic for rickets and osteomalacia
< 2.4mmol/l
43
in some cases of rickets and osteomalacia another investigation is needed - what is this ?
bone biopsy