Metabolic bone disease: histopathology

Question 1

Functions of bone: 
• STRUCTURE – 
• MECHANICAL – 
• PROTECTIVE – 
• METABOLIC –

Answer 1

• 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 mineral

Question 2

The composition of bone
• INORGANIC -65% –
• ORGANIC -35% –

Answer 2

• INORGANIC -65% – calcium hydroxyapatite (Ca10(PO4)6(OH)2) – is storehouse for 99% of Calcium in the body – 85% of the Phosphorus, 65% Sodium, Magnesium
• ORGANIC -35% – bone cells and protein matrix

Question 3

bone geography

Answer 3

look at the bones and label

Question 4

what are the bone types/classifications?
• 3 types
• describe each one

Answer 4

• Anatomical bones
-Flat, long, short/cuboid, irregular, sesamoid
• Macroscopic structure – trabecular/cancellous/spongy – cortical/compact
• Microscopic structure – Woven bone (immature) – Lamellar bone (mature)

Question 5

what are the two classification of bones?

Answer 5

CORTICAL 
• long bones 
• 80% of skeleton 
• appendicular 
• 80-90% calcified 
• mainly structural, mechanical, and protective 

CANCELLOUS
• vertebrae & pelvis 
• 20% of skeleton 
• axial 
• 15-25% calcified 
• mainly metabolic 
• large surface area

Question 6

learn cortical bone microanatomy

Answer 6

see slides

Question 7

Name three types of bone cells and what they do:

Answer 7

• Osteoclasts - multinuclear cells that resorb/remove bone
• Osteoblasts - produce osteoid to form new bone
• Osteocytes - mechanosensory network embedded in mature bon

Question 8

why perform a bone biopsy?

Answer 8

• Confirm the diagnosis of a bone disorder
• Find the cause of or evaluate ongoing bone pain or tenderness
• Investigate an abnormality seen on X-ray
• For bone tumour diagnosis (benign vs malignant)
• To determine the cause of an unexplained infection
• To evaluate therapy performance

Question 9

what are the types of bone biopsy?

Answer 9

• Closed – needle -core biopsy (Jamshidineedle)

* Open –for sclerotic / inaccessible lesion

Question 10

what are the histological stains?

Answer 10

• H & E
• Masson -Goldner Trichrome
• Tetracycline/Calceinlabellin

Question 11

what is metabolic bone disease?
What is it due to?
What does it cause?

Answer 11

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)
• Cause altered bone cell activity, rate of mineralisation, or changes in bone structure

Question 12

Give some examples of common metabolic bone disease:

Answer 12

• Osteoporosis
• Osteomalacia/Rickets • Primary hyperparathyroidism
• Renal osteodystrophy
• Paget’s disease

Question 13

Define osteoporosis

Two types

Answer 13

• Defined as a bone mineral density T-score of -2.5 or lower – Standard deviations different from mean peak bone mass BMD
• 1º -age, post-menopause • 2º -drugs, systemic disease
• High turnover vs low turnover

Question 14

what is osteomalacia?

What are the two types?

Answer 14

• Defective mineralisation of normally synthesized bone matrix
• Rickets in children
• Effectively 2 types – Deficiency of vitamin D – Deficiency of PO

Question 15

Osteomalacia-Sequelae

Answer 15

Osteomalacia-Sequelae

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

Question 16

what is hyperparathyroidism

Answer 16

Excess PTH
• increased Ca + PO4 excretion in urine 
• hypercalcaemia 
• hypophosphatemia 
• skeletal changes of osteitis fibrosa cystica

Question 17

Which 4 organs are directly affected in hyperparathyroidism?

Answer 17

• 4 organs are directly or indirectly affected by PTH and between them control Calcium metabolism • Parathyroid glands • Bones • Kidneys • Proximal small intestine

Question 18

What is primary and secondary hyperparathyroidism caused by?

Answer 18

• 1º – parathyroid adenoma (85-90%) – chief cell hyperplasia

* 2º – chronic renal deficiency – vit D deficiency

Question 19

Symptoms for hyperparathyroidism

Answer 19

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

Question 20

What does renal osteodystrophy do?

Answer 20

Comprises all the skeletal changes resulting from chronic renal disease:
– Increased bone resorption (osteitis fibrosa cystica)
– Osteomalacia
– Osteosclerosis
– Growth retardation
– Osteoporosis

Question 21

What is paget’s disease?

Answer 21

Disorder of bone turnover

Question 22

what are the three stages of paget’s disease?

Answer 22

Divided into 3 stages

1. Osteolytic
2. Osteolytic-osteosclerotic
3. Quiescent osteosclerotic

Question 23

Epidemiology of paget’s disease

Answer 23

Onset > 40y (affects 3-8% Caucasians > 55y) M>F
Rare in Asians and Africans Mono-ostotic15%
Remainder polyostoti

Question 24

Aetiology of Paget’s disease

Answer 24

Aetiology is unknown Familial cases show autosomal pattern of inheritance with incomplete penetrance (mutations in SQSTM1 or RANK) Parvomyxovirustype particles have been seen on EM in Pageticbone –some doubt this is cause. Overuse or previous bone injury

Question 25

clinical symptoms of paget’s disease

Answer 25

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