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eLCRS - 머크 > 1 Metabolic Bone Disease: Histopathology > Flashcards

1 Metabolic Bone Disease: Histopathology Flashcards

1
Q

What are the 4 functions of bone?

A
  • structural function = gives structure + shape to body
  • mechanical function = acts as site for muscle attachment
  • Protects vital organs + bone marrow
  • Metabolic function = acts as a reserve for calcium and other minerals
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2
Q

Describe the composition of bone

organic = \_\_\_% 
inorganic = \_\_\_%
A

organic = 35 %
- contains bone cells + protein matrix

inorganic = 65 %

  • contains calcium hydroxyapatite crystals
  • stores 99% of calcium in body
  • stores P (85%), Na (65%), Mg
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3
Q

what is the difference between cortical + cancellous bone?

A
  • Cortical:
  • Long bones
  • 80% of skeleton
  • Appendicular
  • 80-90% calcified
  • Mainly mechanical + protective
  • Cancellous (trabecular):
  • in BM
  • Vertebrae + pelvis
  • 20% of skeleton
  • Axial skeleton
  • 15-25% calcified
  • Mainly metabolic –> high turnover (can quickly release mineral)
  • Large SA
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4
Q

When would you perform bone biopsy?

A

Indications/uses:
- To confirm diagnosis of bone disorder

  • to find cause of bone pain/ tenderness
  • to Investigate abnormality seen on X-ray
  • For bone tumour diagnosis (benign or malignant)
  • To Determine cause of unexplained infection
  • To Evaluate therapy performance
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5
Q

What are the 2 types of bone biopsy?

A
  1. closed (needle)
  2. open
    - -> for sclerotic/inaccessible lesions
    - -> under general anesthesia
    - -> removal of chunk of bone
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6
Q

What are the 3 different types of bone cells?

A
  1. osteoblasts
  2. osteoclasts
  3. osteocytes
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7
Q

what do the osteoblasts do?

A

builds bones by laying down osteoid

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8
Q

what do the osteoclasts do?

A

multinucleate cell of macrophage family that resorbs/ removes bone

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9
Q

what do the osteocytes do?

A
  • osteoblast like cells

- sits in bone lacunae

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10
Q

what happens when RANK binds to RANKL?

A
  • it causes osteoclast precursor cells to differentiate –> and increase bone resorption
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11
Q

What does OPG do?

A

OPG = osteoprotegerin

  • outcompetes with RANK for RANKL
  • inhibits RANK-RANKL binding
  • -> inhibiting osteoclastogenesis
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12
Q

what is meant by metabolic bone disease?

A
  • disordered bone turnover due to an imbalance of various chemicals in the body
    e. g vitamins, hormones, minerals

–> causes altered bone cell activity / rate of mineralization / change in bone structure

  • overall effect = osteopaenia
  • -> often leads to fracture with little/no trauma
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13
Q

define osteopaenia

A
  • reduced bone mass
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14
Q

What are the 3 main categories of metabolic bone disease?

A
  1. Endocrine abnormality (Vit D deficiency, PTH-excess)
  2. Non-endocrine (e.g. age-related osteoporosis)
  3. Disuse osteopenia (when don’t use legs so much, bones weaker)
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15
Q

What is the difference between primary and secondary osteoporosis?

A

1º - age, post-menopause

2º - drugs, systemic disease

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16
Q

define osteomalacia

A

defective bone mineralization of normally synthesized bone matrix

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17
Q

what are the 2 types of osteomalacia?

A
  1. Deficiency of vitamin D

2 Deficiency of PO4

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18
Q

What complications can occur due to osteomalacia?

i.e describe the sequelae of osteomalacia

A

Sequelae of osteomalacia =

  • bone pain/tenderness
  • fracture
  • proximal weakness
  • bone deformity
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19
Q

describe biochemical changes in hyperparathyroidism

increase/decrease
PTH =
Ca2+ excretion =
PO4 excretion =

A

PTH = excess
Ca2+ excretion = increased
PO4 excretion = increased

20
Q

hyperparathyroidism leads to :

A
  • hypercalcaemia
  • hypophosphataemia
  • increased excretion of phosphate + calcium
  • osteitis fibrosa cystica
21
Q

what are the 4 organs indirectly/directly affected by PTH?

A
  • Parathyroid glands
  • Bones
  • Kidneys
  • Proximal small intestine
22
Q

What is the difference between causes of primary and secondary hyperparathyroidism?

A

Primary causes:

  • adenoma (majority)
  • chief cell hyperplasia

Secondary causes:

  • chronic renal deficiency
  • Vit D deficiency (mainly)
23
Q

what are symptoms of hyperparathyroidism?

A
  • Stones
    (Calcium oxalate renal stones)
  • Bones
    (osteitis fibrosa cystica, bone resorption)
  • Abdominal groans
    (acute pancreatitis)
  • Psychic moans
    (psychosis & depression)
24
Q

Brown cell tumours = seen in hyper/hypoparathyroidism, formed by osteoclast/blast cell groups

A

Brown cell tumours = seen in hyperparathyroidism, formed by osteoclast cell groups

25
Q

what is renal osteodystrophy?

A
  • all skeletal changes of chronic renal disease:
  1. Increased bone resorption (osteitis fibrosa cystica)
  2. Osteomalacia
  3. Osteosclerosis
  4. Growth retardation
  5. Osteoporosis
26
Q

What are comorbidities associated with renal osteodystrophy ?

A
  • hyperphosphataemia
  • Hypocalcaemia
    (as a result of ↓vit D)
  • Secondary hyperparathyroidism
  • Metabolic acidosis
  • Aluminium deposition
27
Q

What are the 3 stages of Paget’s disease?

A
  1. Osteolytic
  2. Osteolytic-osteosclerotic (mixed phase)
  3. Quiescent osteosclerotic
28
Q

Paget’s Disease Notes:

  • More common in whites (rare in Asians/Africans)
  • develops over 40,
  • same freq. in M + F,
  • mostly asymptomatic

o 85% polyostotic (multiple bones affeceted) , 15% mono-ostotic (1 bone affected)

A

-

29
Q

Paget’s disease =

Common/ Rare in fingers or toes,

usually _/_vertebrae (most common), skull, pelvis, lower limbs e.g. tibia

A

Rare in fingers or toes,

usually T/L vertebrae (most common), skull, pelvis, lower limbs e.g. tibia

30
Q

What are clinical symptoms of Paget’s disease?

A

o Pain

o Microfractures (spontaneous) + deformity

o Nerve compression due to new bone formation, spinal stenosis

o Skull changes may put medulla at risk

o Deafness

o Possible haemodynamic changes, cardiac failure

o Hypercalcaemia

o Osteogenic sarcoma in area of involvement (1%)

31
Q

describe + Identify bone geography

  • epiphysis
  • diaphysis
  • periosteum
  • cortex
  • medulla
  • metaphysics
  • epiphyseal line
  • subchondral bone
A

-

32
Q

note: to show up on X-ray bones need to be 50% mineralized

A

-

33
Q

5 diff types of anatomical bones

A
  • flat
  • long (e.g tibia)
  • short/cuboid (carpals)
  • irregular bones (e.g pelvis/ vertebrae)
  • sesamoid (patellar –> has protective functions)
34
Q

what is the 2 diff macroscopic classification of bone

A
  • trabecular/ cancellous/ spongy

- cortical / compact

35
Q

what is the 2 diff microscopic classification of bone

A
  • woven bone (weaker) - immature

- lamellar bone - mature

36
Q

identify different parts of the cortical bone micro anatomy

A

-

37
Q

note: immature woven bone = disorganized

mature bone = striae is visible

A

refer to slides for microscopic diagrams of bone parts

38
Q

describe the bone remodeling cycle

A
  • osteocytes - forms when they are signaled by apoptosis of osteocytes which forms RANKL
  • which is stimulated to form mature osteoclasts
    that differentiate into reversal cells
39
Q

typical site for bone biopsy =

A

transiliac bone biopsy

40
Q

what are the 3 different histological stains for the bone biopsy ?

what are they used for?

A
  • H&E stains
  • Masson Goldner trichrome stain = labels unmineralized (orange) + mineralized (green) bone
  • tetracycline / calcein labelling = looks at bone turnover
    (difference btw 2 lines –> shows difference in bone formation)
41
Q

define osteoporosis

A

bone mineral density T score <2.5

42
Q

high turnover osteoporosis
vs
low turnover osteoporosis

A

high turnover osteoporosis
**

low turnover osteoporosis
decrease in bone formation greater than decreased bone resorption

43
Q

what might you see in a microscopic biopsy of osteoporosis?

A

thinner trabeculae

thinning of cortical bone

44
Q

what bone change might you observe in hyperparathyroidism ?

A
  • subperiosteal bone erosions
  • tunnelling erosion
  • brown cell tumors
45
Q

Note = paget’s disease:
early stages= high turnover
later = goes on to form disorganized bone

A

-

eLCRS - 머크 (9 decks)

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