Metabolic Bone disease - Histopathology Flashcards
What are the functions of bone
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
Describe the composition of bone
65% inorganic
Calcium hydroxyapatite
Storehouse for 99% of body’s calcium. Also stores phosphorus, sodium and magnesium
35% organic
Bone cells and protein matrix
Describe the structure of bone
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
What are the anatomical types of bone and give examples of each
Flat - skull Long - femur Short/cuboid - carpals Irregular - vertebrae Sesamoid - patella
What are the macroscopic structure classifications of bone
Trabecular/cancellous/spongy
Cortical/compact
What are the microscopic classifications of bone
Woven bone (immature) Lamellar bone (mature)
Describe cortical bone
Long bones 80% of the skeleton Appendicular 80-70% calcified Mainly structural. mechanical and protective
Describe cancellous bone
Vertebrae and pelvis 20% of the skeleton Axial 15-25% calcified Mainly metabolic Large surface area
Describe osteoclasts
Multinuclear cells that resorb/remove bone
Describe osteoblasts
Produce osteoid to form new bone
Describe osteocytes
Mechanosensory network embedded in mature bone
Describe what occurs in the bone remodelling cycle
- Damage to bone is sensed by osteocytes
- Monocytes differentiate into osteoclast precursors
- RANKL is released from pre-osteoblasts
- M-CSF is released from osteoblasts
- Maturation of osteoclasts via RANKL and M-CSF
- Osteoclastic bone resorption
- Reversal via reversal cells
- Osteoblastic bone formation
Why would you perform a bone biopsy
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
What are the types of bone biopsy
Closed - Jamshidi needle - core biopsy
Open - for sclerotic/inaccessible lesions
What are the histological stains used for bone
H + E
Masson - Goldner trichrome
Tetracycline/calcein labelling
What is the H+E stain used for in bone
Shaft of long bone
Articular surface
Bone cells
Stains purple
What is the Masson - Goldner trichrome stain used for in bone
Un-mineralised osteoid stains orange
What is Tetracycline/calcein labelling used for in bone
Good to determine whether bone remodelling is fast or slow
What is metabolic bone disease and what is it due to
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)
What do metabolic bone disease cause
Altered bone cell activity, rate of mineralisation, or changes in bone structure
What is the definition of osteoporosis
Bone mineral density T-score of -2.5 or lower
High turnover vs low turnover
What are the primary and secondary causes of osteoporosis
Primary - age, post-menopause
Secondary - drugs, systemic disease
What are the histopathological features of osteoporosis
Trabeculae thinner
Few trabeculae
“Free-floating” trabeculae i.e. disconnected
What is osteomalacia
Defective mineralisation of normally synthesised bone matrix
Rickets in children
2 types: Vit D deficiency, PO4 deficiency
What are the histopathological features of osteomalacia
Very large areas of un-mineralised bone.
Masson-Goldner Trichrome will have large orange areas
What is the sequelae of osteomalacia
bone pain/tenderness
fracture
proximal weakness
bone deformity
What is hyperparathyroidism and what are its features
Excess PTH
Increased Ca + PO4 excretion in urine
Hypercalcaemia
Hypophosphataemia
Skeletal changes of osteitis fibrosa cystica
Which organs are directly/indirectly affected by PTH
Parathyroid glands
Bones
Kidneys
Proximal Small intestine
What are the causes of primary hyperparathyroidism
parathyroid adenoma (85-90%)
chief cell hyperplasia
What are the causes of secondary hyperparathyroidism
Chronic renal deficiency
Vit D deficiency
What are the signs and symptoms of hyperparathyroidism
Stones (Caoxalaterenalstones)
Bones (osteitisfibrosacystica,boneresorption)
Abdominal groans (acutepancreatitis)
Psychic moans (psychosis & depression)
What are the histopathological features of hyperparathyroidism
Trabeculae central channel is removed
What is a brown cell tumour
-
What is renal osteodystrophy
Comprises all skeletal changes resulting from chronic renal disease
- Increased bone resorption (osteitis fibrosa cystica)
- Osteomalacia
- Osteosclerosis
- Growth retardation
- Osteoporosis
What are the 3 stages of Paget’s disease
- Osteolytic
- Osteolyic-osteosclerotic
- Quiscent osteosclerotic
Describe the epidemiology of paget’s
Onset > 40y (affects 3-8% Caucasians > 55y) M>F Rare in Asians and Africans Mono-ostotic 15% Remainder polyostotic
What are the clinical symptoms of Paget’s diseas
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%
What are the histopathological features of Paget’s disease
Loss of trabeculae
Quiescent osteosclerotic - Mosaic pattern
