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Y2 Musculoskeletal > Metabolic Bone disease - Histopathology > Flashcards

Metabolic Bone disease - Histopathology Flashcards

1
Q

What are the functions of bone

A

Structure - give structure and shape to the body
Mechanical - Sites for muscle attachment
Protective - vital organs and bone marrow
Metabolic - Reserve of calcium and other minerals

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2
Q

Describe the composition of bone

A

65% inorganic
Calcium hydroxyapatite
Storehouse for 99% of body’s calcium. Also stores phosphorus, sodium and magnesium

35% organic
Bone cells and protein matrix

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3
Q

Describe the structure of bone

A

Diaphysis (shaft), followed by metaphyses and epiphyses

Spongy bone that is covered by a layer of compact bone and a layer of periosteum
Bone marrow found in the diaphysis
Growth plates and trabecular bone found in the metaphysis

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4
Q

What are the anatomical types of bone and give examples of each

A 
Flat - skull
Long - femur
Short/cuboid - carpals
Irregular - vertebrae
Sesamoid - patella
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5
Q

What are the macroscopic structure classifications of bone

A

Trabecular/cancellous/spongy

Cortical/compact

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6
Q

What are the microscopic classifications of bone

A 
Woven bone (immature)
Lamellar bone (mature)
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7
Q

Describe cortical bone

A 
Long bones 
80% of the skeleton 
Appendicular
80-70% calcified 
Mainly structural. mechanical and protective
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8
Q

Describe cancellous bone

A 
Vertebrae and pelvis 
20% of the skeleton 
Axial 
15-25% calcified 
Mainly metabolic 
Large surface area
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9
Q

Describe osteoclasts

A

Multinuclear cells that resorb/remove bone

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10
Q

Describe osteoblasts

A

Produce osteoid to form new bone

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11
Q

Describe osteocytes

A

Mechanosensory network embedded in mature bone

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12
Q

Describe what occurs in the bone remodelling cycle

A
  1. Damage to bone is sensed by osteocytes
  2. Monocytes differentiate into osteoclast precursors
  3. RANKL is released from pre-osteoblasts
  4. M-CSF is released from osteoblasts
  5. Maturation of osteoclasts via RANKL and M-CSF
  6. Osteoclastic bone resorption
  7. Reversal via reversal cells
  8. Osteoblastic bone formation
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13
Q

Why would you perform a bone biopsy

A

Confirm diagnosis of a bone disorder
Find the cause/evaluate ongoing bone pain or tenderness
Investigate an abnormality on X ray
Bone tumour diagnosis
Determine the cause of an unexplained infection
Evaluate therapy performance

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14
Q

What are the types of bone biopsy

A

Closed - Jamshidi needle - core biopsy

Open - for sclerotic/inaccessible lesions

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15
Q

What are the histological stains used for bone

A

H + E
Masson - Goldner trichrome
Tetracycline/calcein labelling

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16
Q

What is the H+E stain used for in bone

A

Shaft of long bone
Articular surface
Bone cells

Stains purple

17
Q

What is the Masson - Goldner trichrome stain used for in bone

A

Un-mineralised osteoid stains orange

18
Q

What is Tetracycline/calcein labelling used for in bone

A

Good to determine whether bone remodelling is fast or slow

19
Q

What is metabolic bone disease and what is it due to

A

A group of diseases that cause reduced bone mass and reduced bone strength

Due to imbalance of various chemicals in the body (vitamins, hormones, minerals, etc)

20
Q

What do metabolic bone disease cause

A

Altered bone cell activity, rate of mineralisation, or changes in bone structure

21
Q

What is the definition of osteoporosis

A

Bone mineral density T-score of -2.5 or lower

High turnover vs low turnover

22
Q

What are the primary and secondary causes of osteoporosis

A

Primary - age, post-menopause

Secondary - drugs, systemic disease

23
Q

What are the histopathological features of osteoporosis

A

Trabeculae thinner
Few trabeculae
“Free-floating” trabeculae i.e. disconnected

24
Q

What is osteomalacia

A

Defective mineralisation of normally synthesised bone matrix
Rickets in children
2 types: Vit D deficiency, PO4 deficiency

25
Q

What are the histopathological features of osteomalacia

A

Very large areas of un-mineralised bone.

Masson-Goldner Trichrome will have large orange areas

26
Q

What is the sequelae of osteomalacia

A

bone pain/tenderness
fracture
proximal weakness
bone deformity

27
Q

What is hyperparathyroidism and what are its features

A

Excess PTH

Increased Ca + PO4 excretion in urine
Hypercalcaemia
Hypophosphataemia
Skeletal changes of osteitis fibrosa cystica

28
Q

Which organs are directly/indirectly affected by PTH

A

Parathyroid glands
Bones
Kidneys
Proximal Small intestine

29
Q

What are the causes of primary hyperparathyroidism

A

parathyroid adenoma (85-90%)

chief cell hyperplasia

30
Q

What are the causes of secondary hyperparathyroidism

A

Chronic renal deficiency

Vit D deficiency

31
Q

What are the signs and symptoms of hyperparathyroidism

A

Stones (Caoxalaterenalstones)

Bones (osteitisfibrosacystica,boneresorption)

Abdominal groans (acutepancreatitis)

Psychic moans (psychosis & depression)

32
Q

What are the histopathological features of hyperparathyroidism

A

Trabeculae central channel is removed

33
Q

What is a brown cell tumour

A

-

34
Q

What is renal osteodystrophy

A

Comprises all skeletal changes resulting from chronic renal disease

  • Increased bone resorption (osteitis fibrosa cystica)
  • Osteomalacia
  • Osteosclerosis
  • Growth retardation
  • Osteoporosis
35
Q

What are the 3 stages of Paget’s disease

A
  1. Osteolytic
  2. Osteolyic-osteosclerotic
  3. Quiscent osteosclerotic
36
Q

Describe the epidemiology of paget’s

A 
Onset > 40y (affects 3-8% Caucasians > 55y) 
M>F
Rare in Asians and Africans
Mono-ostotic 15%
Remainder polyostotic
37
Q

What are the clinical symptoms of Paget’s diseas

A

Pain
Microfractures
Nerve compression (incl. Spinal N and cord)
Skull changes may put medulla at risk
Deafness
+/- haemodynamic changes, cardiac failure
Hypercalcaemia
Development of sarcoma in area of involvement 1%

38
Q

What are the histopathological features of Paget’s disease

A

Loss of trabeculae

Quiescent osteosclerotic - Mosaic pattern

Y2 Musculoskeletal (9 decks)

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