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Musculoskeletal > Bone Disease - Histopathology > Flashcards

Bone Disease - Histopathology Flashcards

1
Q

What are the main functions of bones?

A

Mechanical – support and shape body
Site for muscle attachment
Protective
Metabolic – reserve of calcium

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2
Q

What are the two main components of bone and what are their relative proportions?

A

Inorganic (65%) – calcium hydroxyapatite stores 99% of body’s Ca, 85% of the P and 65% of Na and Mg

Organic (35%) – bone cells and protein matrix

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3
Q

Describe the classification of bone as cortical and cancellous.

A 
Cortical - 
Long bones 
80% of skeleton  
Appendicular skeleton 
80-90% calcified 
Mainly mechanical and protective role 
Cancellous - 
Vertebrae and pelvis 
20% of skeleton 
Axial 
15-25% calcified
Mainly metabolic  
Large surface
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4
Q

What are the indications for bone biopsy?

A 
Evaluate bone pain or tenderness 
Investigate abnormality seen on X-ray 
Bone tumour diagnosis 
Determine cause of unexplained infection 
Evaluate therapy
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5
Q

What are the two types of bone biopsy?

A

Closed – core biopsy with Jamshidi needle

Open – surgical removal under general anaesthetic (for sclerotic or inaccessible lesions)

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6
Q

What are the three types of bone cell?

A

Osteoblast – build bone by laying down osteoid Osteoclast – multinucleate cells of the macrophage family that resorb bone
Osteocyte – osteoblast like cells, form network for signalling in bone (for repair etc.)

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7
Q

Where are osteocytes found?

A

Lacunae

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8
Q

What cytokine is important for stimulating the differentiation of osteoclast precursors into pre-osteoclasts?

A

M-CSF (produced by osteoblasts)

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9
Q

Which cells produce RANKL and what is its effect?

A

Pre-osteoblasts

It stimulates the maturation of osteoclasts

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10
Q

What do mature osteoblasts produce that blocks the RANK/RANKL binding?

A

Osteoprotegerin

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11
Q

How are bones classified anatomically?

A 
Flat - E.g Ribs
Long - E.g Femur
Cuboid - Carpals, Tarsals 
Irregular bones - Very specifically shaped, e.g Pelvis
Sesamoid - Inserted within a tendon
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12
Q

What type of ossification leads to the formation of long and flat Bones.

A

Long bones = Endochondral ossification

Flat bones = Intramembranous ossification

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13
Q

How else can bone be classified?

A

Trabecular (cancellous) or compact (cortical)

Woven (immature) or lamellar (mature)

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14
Q

What is metabolic bone disease?

A

Disordered bone turnover due to imbalance of various chemicals in the body (vitamins, hormones, minerals etc.)

Overall effect is usually reduced bone mass (osteopaenia) often resulting in fractures from little or no trauma

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15
Q

What are the three main categories of metabolic bone disease?

A

Related to endocrine abnormality (e.g. Vit D and PTH)

Non-endocrine (e.g. age-related osteoporosis)

Disuse osteopaenia

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16
Q

Describe the staining of calcified and uncalcified bone.

A

Calcified – green

Uncalcified – orange

17
Q

What are the primary and secondary causes of osteoporosis?

A

Primary
Age
Post-menopause

Secondary
Drugs
Systemic disease

18
Q

Describe the histology of osteoporotic bone.

A

Weak trabecular bridging

Holes and cysts

19
Q

What is osteomalacia and what can it be caused by?

A

Condition of defective bone mineralisation that can be caused by Vitamin D deficiency or Phosphate deficiency (usually related to chronic renal disease)

20
Q

What are the metabolic and endocrine consequences of vitamin D deficiency?

A

Secondary hyperparathyroidism –> increased bone resorption

Hypocalcaemia – neuronal excitability causing muscle twitching, spasms, tingling and numbness

21
Q

Describe the histology of osteomalacia.

A

No calcification of bone
More uncalcified osteoid
Bones are very bendy and cannot carry musculature very easily

22
Q

What are the clinical consequences of osteomalacia?

A

Bone pain/tenderness
Fracture (horizontal fractures at Looser’s zone at the neck of the femur are commonly seen)
Proximal weakness
Bone deformity

23
Q

What is used to investigate mineralisation?

A

Fluorescent tetracycline labelling

24
Q

What are the consequences of hyperparathyroidism?

A

Hypercalcaemia (increased Ca2+ reabsorption)
Hypophosphataemia (increased phosphate excretion in the urine)
Osteitis fibrosa cystica (due to increased osteoclast activity)

25
Q

List the four organs that are directly or indirectly affected by parathyroid hormone to control calcium metabolism.

A

Parathyroid glands
Bones
Kidneys
Proximal small intestine

26
Q

State some causes of primary hyperparathyroidism.

A

Parathyroid adenoma

Chief cell hyperplasia

27
Q

State some causes of secondary hyperparathyroidism.

A

Chronic renal insufficiency

Vitamin D deficiency

28
Q

What are the symptoms of hyperparathyroidism?

A

Stones, Bones, Abdominal Groans and Psychic Moans

Stones – calcium oxalate renal stones
Bones – osteitis fibrosa cystica
Abdominal Groans – acute pancreatitis
Psychic Moans – psychosis and depression

29
Q

What is the most important investigation for hyperparathyroidism and what will it show in someone with hyperparathyroidism?

A

X-ray of the hand Subperiosteal bone erosions Brown cell tumours – small areas of resorption in the long bones of the fingers that are filled with osteoclasts

30
Q

What are the five features of renal osteodystrophy?

A 
Increased bone resorption (osteitis fibrosa cystica) 
Osteomalacia 
Osteoporosis 
Osteosclerosis 
Growth retardation
31
Q

What are the consequences of renal osteodystrophy?

A 
Hyperphosphataemia 
Hypocalcaemia as a result of a decrease in vitamin D metabolism 
Secondary hyperparathyroidism 
Metabolic acidosis 
Aluminium deposition
32
Q

What is Paget’s disease?

A

Disorder of bone turnover (there is a lack of proper communication between the cells)

33
Q

What are the three stages of Paget’s disease?

A

Osteolytic
Osteolytic-osteosclerotic
Quiescent osteosclerotic

34
Q

Describe the histology of Paget’s disease.

A

Prominent reversal lines Masses of osteoclasts in the same site as osteoblasts

35
Q

In which ethnicities is Paget’s disease almost non-existant?

A

Asian, African

Most commonly present in Caucasians

36
Q

Which sites does Paget’s disease most commonly affect?

A 
Skull 
Sternum 
Spine 
Humerus 
Pelvis 
Femur 
Tibia
37
Q

List some clinical features of Paget’s disease.

A 
Pain 
Microfractures 
Nerve compression 
Skull changes 
Deafness 
Haemodynamic changes 
Cardiac failure 
Hypercalcaemias 
Development of sarcoma in the area of involvement
38
Q

What is a Haversian canal?

A

Channel that blood vessels run in within bone

39
Q

What are Howship’s Lacunae?

A

Pits in the bone surface where osteoclasts are found (also called resorption bays)

Musculoskeletal (8 decks)

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