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MSK (Medicine 2: Year 2) > Metabolic Bone Disease > Flashcards

Metabolic Bone Disease Flashcards

1
Q

What cell makes new bone and which destroys old bone?

A

osteoblasts builds new bone

osteoclasts destroys old bone

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2
Q

What is the main thing that regulates bone remodelling cycles?

A

mainly osteoblast being stimulated by:

  • TNF alpha
  • IL-1
  • IL-11
  • Vitamin D
  • Glucocorticoids
  • PTH
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3
Q

Describe vitamin D metabolism?

A
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4
Q

What is the main storage form of vitamin D and where is it found?

A

25(OH)vit D, and is found in liver, adipose tissue and muscle

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5
Q

What is the main function of vitamin D?

A

to work with PTH to move calcium

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6
Q

What are risk factors for vitamin D deficiency?

A
  • Liver disease
  • Kidney disease
  • Darker skin
  • Increased age
  • Time of year/where we live (further away from equator)
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7
Q

Describe the hormonal regulation of vitamin D?

A

Ca absorbed from gut with vitamin D; moves in and out of bone under action of PTH

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8
Q

ECF calcium levels are kept within tight parameters at the expense of what?

A

calcium within bone

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9
Q

Where are most of the bodies calcium stores found?

A

Within bone

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10
Q

What is Paget’s disease?

A

Localised disorder of bone turnover where there is:

  • Increased bone resorption followed by increased bone formation
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11
Q

What changes does Paget’s disease cause in bone?

A
  • Leads to disorganised bone which is
    • Bigger, less compact, more vascular and more susceptible to deformity and fracture
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12
Q

What is the aetiology for Paget’s disease?

A
  • genetics: loci of SQSTMI
  • environmental: geographical distribution, chronic viral infection
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13
Q

Describe the clinical presentation of Paget’s disease?

A
  • Always over 40 years
  • Bone pain
  • Bone deformity
  • Excessive heat over Pagetic bone
  • Neurological complications such as nerve deafness
  • Elevation of alkaline phosphatase on blood tests
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14
Q

What is elevated in blood tests for Paget’s disease?

A
  • Elevation of alkaline phosphatase on blood tests
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15
Q

What is the treatment for Paget’s disease?

A

IV bisphosphonate therapy - one off zoledronic acid infusion

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16
Q

What is rickets and osteomalacia?

A

Severe nutritional vit D or calcium deficiency causing insufficient mineralisation causes:

  • Rickets (growing child)
  • Osteomalacia (adult) when epiphyseal plates are closed
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17
Q

Does rickets and osteomalacia affect children or adults?

A

Rickets - children

Osteomalacia - adults

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18
Q

What is the presentation of rickets?

A
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19
Q

What are risk factors for osteomalacia?

A
  • Elderly
  • Darker skin
20
Q

What is the treatment for rickets?

A
  • Calcium and vitamin D supplements
21
Q

What is the presentation of osteomalacia?

A
  • Bone pain
  • Muscles weakness
  • Increased falls risk
22
Q

What investigation should be done for osteomalacia?

A
  • X-ray
    • Can see micro fractures
23
Q

What is the treatment for osteomalacia?

A
  • Vitamin D and calcium supplements
24
Q

What does OI stand for?

A

Osteogenesis imperfecta

25
Q

What is osteogenesis imperfecta (OI)?

A

Is a genetic disorder of connective tissue (type 1 collagen) characterised by fragile bones from mild trauma and even acts of daily life

26
Q

Genetic disorder of what connective tissue causes OI?

A

Type 1 collagen

27
Q

How many genetic types of OI are there?

A

8 different genetic types, 4 of which are most common:

type 1: milder form, often when child starts to walk and can present in adults

type 2: lethal by age 1, most severe form

type 3: progressive deformity with severe bone dysplasia and poor growth

type 4: similar to type 1 but more severe

28
Q

What are the 4 most common genetic types of OI?

A
  • Type 1
    • Milder form, often when child starts to walk and can present in adults
  • Type 2
    • Lethal by age 1, most severe form
  • Type 3
    • Progressive deformity with severe bone dysplasia and poor growth
  • Type 4
    • Similar to type 1 but more severe
29
Q

What is the presentation of osteogeneis imperfecta?

A
  • Growth deficiency
  • Defective tooth formation
  • Hearing loss
  • Blue sclera
  • Scoliosis/barrel chest
  • Ligamentous laxity
  • Easy bruising
  • Hypermobility
30
Q

What score can be used to assess hypermobility?

A

Beighton score

31
Q

What is the mangement of OI?

A
  • Surgical
    • Treat fractures
  • Medical
    • To prevent fracture, IV bisphosphonates
  • Social
    • Educational and social adaptions
  • Genetic
    • Genetic counselling for parents and next generation
32
Q

What is OI characterised by?

A

Characterised by fragile bones from mild trauma and even acts of daily life

33
Q

What is osteoporosis?

A

Is a metabolic bone disease characterised by low bone mass and micro architectural deterioration of bone tissue:

  • Causes enhanced bone fragility and consequent increase in fracture
  • Also defined as on DXA bone scan
34
Q

How is osteoporosis defined on a bone scan?

A
  • Also defined as on DXA bone scan
35
Q

What is risk of fracture related to?

A
  • Bone density and how thick bone is
  • Age
  • How likely to fall
  • Bone turnover
36
Q

How can risk of fracture be assessed?

A

using online tools such as FRAX or Q fracture

37
Q

What investigation should be done for osteoporosis?

A
  • DEXA scanner (DXA scan)
    • Examine L1 to L4 on spine for BMD (bone density)
      • Better for younger people
    • Examine left and right hip
      • Better for older people
    • Lateral DXA scan for vertebral fractures
    • Look at T score which is number of SDs below matched young person (except age, so same sex and ethnicity and BMI), each 1 SD below is 2x risk
    • Z score compares patient to matched patient of same age as well
38
Q

What are the T and Z scores on a bone scan?

A
  • Look at T score which is number of SDs below matched young person (except age, so same sex and ethnicity and BMI), each 1 SD below is 2x risk
  • Z score compares patient to matched patient of same age as well
39
Q

1SD below on a DEXA scan represents what?

A

2x risk

40
Q

When should patients be referred to a DEXA scan after fracture risk assessment?

A
  1. Risk assessment online tool
  2. If risk is >10% of osteoporotic fracture over 10 years refer for DXA scan
    1. Anyone on oral steroids should be referred regardless of score
41
Q

Does osteoporosis affect more males or females?

A

F>M

42
Q

What are some causes of osteoporosis?

A
  • Endocrine causes
    • Thyrotoxicosis
    • Hyper and hypoparathyroidism
    • Cushings
    • Hyperprolactinaemia
    • Hypopituitarism
    • Low sex hormone levels
  • Rheumatic causes
    • Rheumatoid arthritis
    • Ankylosing spondylitis
    • Polymyalgia rheumatic
  • Gastroenterological causes
    • Inflammatory diseases (UC and Crohn’s)
    • Liver disease (PBC, CAH, alcoholic cirrhosis, viral cirrhosis)
    • Malabsorption (CF, chronic pancreatitis, coeliac disease, whipples disease, short gut syndromes and ischaemic bowel)
  • Medication causes
    • Steroids
    • Proton pump inhibitors (PPI)
    • Enzyme inducting antiepileptic medications
    • Aromatase inhibitors
    • GnRH inhibitors
    • Warfarin
43
Q

Describe how bone mass changes over time?

A
44
Q

How can osteoporotic fractures be prevented?

A
  • Minimise risk factors
    • Such as smoking, alcohol, diet
  • Ensure good calcium and vitamin D status
  • Falls prevention strategies
  • Medication
45
Q

What medication can be used to prevent osteoporotic fractures?

A
  • Hormone replacement therapy (HRT)
    • Not given to everyone due to side effects
      • Increased risk of blood clots
      • Increased risk of breast cancer
      • Increased risk of heart disease and stroke
  • Selective oestrogen receptor modulator (SERMS)
    • Such as raloxifene
      • Only works on vertebral fractures, not hip and peripheral
      • Side effects includes hot flushes, increased clotting risks
  • Denosumab
    • Monoclonal antibody against RANKL
    • Reduces osteoclastic bone resorption
    • Safer in patients with renal problems than bisphosphonates
    • Side effects includes allergy/rash, systematic hypocalcaemia if given when vitamin D deficient
  • Teriparatide
    • Side effects
      • Injection site irritation
      • Allergy
46
Q

What is the main treatment option for osteoporosis?

A
  • Oral bisphosphonates generally first line of treatment
    • Adequate renal function, calcium and vitamin D status required
    • Mechanism of action is binds to bone mineral, osteoclasts absorbs it and is poisoned, unable to maintain its membrane it becomes stars shaped, recognising itself as being damaged and undergoes apoptosis
    • Side effects
      • Oesophagitis
      • Not safe when eGFR <30mls/min
      • Atypical femoral shaft fractures

MSK (Medicine 2: Year 2) (45 decks)

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