Bones

Question 1

Metabolic bone diseases (5)

Answer 1

Osteoporosis 
Osteomalacia 
Hyperparathyroidism 
Paget's disease 
Renal osteodystrophy

Question 2

Osteoporosis

Answer 2

Age related or due to drugs/disease. 
Decreased bone density. 
  DEXA scan: T > 2.5 SD below mean. 
Low impact fractures, back pain. 
RF: old, woman, smoking, skinny, diet, no oestrogen. 
XR: NAD 
Histology: loss of cancellous bone 
Biochem: NAD.

Question 3

Osteomalacia

Answer 3

Vit D def - dietary, sunlight, malabsorption, genetic.
Reduced bone mineralisation.
Adults: bone pain, prowimal muscle weakness;
Children: bone pain, bowed legs, frontal bossing, pigeon chest, delayed walking.
XR: Looser’s zones (like fractures), splayed metaphyses.
Histology: excess of unmineralised bone (osteoid).
Biochem: low PO4, ^ALP.

Question 4

Hyperparathyroidism

re: bones

Answer 4

^PTH, ^Ca.
Due to adenoma, hyperplasia, carcinoma, MEN.
Osteitis fibrosa cystica.
Sx of ^Ca.
XR: Brown’s tumours, salt and pepper skull, subperiostial bone resorption in phalanges.
Histology: Osteitis fibrosa cycstica =
Biochem: ^Ca, ?^ALP, ?low PO4.

Question 5

Paget’s disease (bone)

Answer 5

Disorder of bone turnover: see both lytic and sclerotic lesions.
Bone pain, big head, microfractures, nerve compression, deafness, high output cardiac failure.
Old white people, no gender bias.
Histology: huge osteoclasts (>100 nuclei), mosaic pattern of lamellar bone.
Biochem: ^^^ALP.

Question 6

Renal osteodystrophy

Answer 6

All the other skeletal changes, with CKD (secondary ^PTH).
Disease features vary wth exact form of bone disease.
Biochem: ^PTH, but ^PO4 and low Ca because renal failure.

Question 7

Non-neoplastic bone diseases (5)

Answer 7

Gout and pseudogout, 
Trauma, 
Osteomyelitis, 
Osteorthritis, 
Rheumatoid arthritis.

Question 8

Gout

Answer 8

Middle aged men.
RF: psoriasis, alcohol, diuretics, inherited metabolic abonormalities.
Affects big toe MTP (podagra), knee.
Tophi are pathagnomonic.
Urate crystals. Needle shape.
Negatively birefriengent in polarised light.
Tx: colchicine in acute, allopurinol long term.

Question 9

Pseudogout

Answer 9

Old. 
Idiopathic.
Knee and shoulder. 
Calcium pyrophosphate crystals. Rhomboid. 
Positively birefringent. 
Tx: NSAIDs or intra-articular steroids.

Question 10

Osteomyelitis

Answer 10

Adults:
Staph aureus, epiphysis, verebrae, dental abscess or diabetic ulcer.
Children:
Haemophilus or GBS, metaphyses of long bones.
Presentation: pain, swelling, fever etc.
XR: Lytic destruction 10 days in.
(Rare causes: TB, syphilis).

Question 11

Malignant Neoplastic bone diseases (4)

Answer 11

Osteosarcoma,
Chondrosarcoma,
Ewing’s sarcoma,
Giant cell (borderline malignancy)

Question 12

Benign bone tumours (7)

Answer 12

Osteoid osteoma, 
Osteoma, 
Enchondroma, 
Ostechondroma, 
Fibrous dyplasia, 
Simple bone cyst, 
Osteoblastoma.

Question 13

Oseosarcoma

Answer 13

Adolescents.
Mostly knee.
Malignant mesenchymal cells with ALP.
XR: elevated periosteum (Codman’s triangle), Sunburst appearance.

Question 14

Ewing’s sarcoma

Answer 14

Adolescents.
Long bones, pelvis.
Sheets of small round cells, CD99 +ve, 11:22 translocn.
XR: onion skinning of periosteum.

Question 15

Giant cell tumour of bone

Answer 15

Women 20-40yo.
Knee epiphysis.
Osteoclast-type multinucleate giant cells on background of spindle/ovoid cells.
XR: lytic (lucent) lesions right up to articular surface.

Question 16

Chondrosarcoma

Answer 16

> 40yo.
Axial skeleton, femur, tibia, pelvis.
Malignant chondrocytes (cartilage).
XR: Lytic lesions with fluffy calcification.