Bones I

Question 1

RANK pathway (2):

Answer 1

• RANKL on osteoblast and marrow stromal cells

- RANK receptor on osteoclast precursor allows osteoclast generation and survival

Question 2

M-CSF Pathway (2):

Answer 2

• M-CSF secreted by osteoblast

- M-CSF receptor allows osteoclast generation and survival

Question 3

WNT/Beta-catenin pathway (3):

Answer 3

• WNT from marrow stromal cells
• LRP5 and LRP6 osteoblast receptor bind WNT protein
• Secrete OPG which blocks RANK

Question 4

Bone composition (2):

Answer 4

• Calcium hydroxyapatite (mineral portion)

- Organic matrix mostly type 1 collagen

Question 5

Osteopontin:

Answer 5

Unique to bone, levels parallel osteoblast activity

Question 6

Alkaline phosphatase:

Answer 6

From osteoblasts, also in liver and placenta

Question 7

Woven bone (4):

Answer 7

• Random collagen deposition
• Rapid bone growth
• Resists forces all directions
• Always pathologic in an adult

Question 8

Lamellar bone (3):

Answer 8

• Ordered collagen deposition
• Replaces woven bone
• Stronger than woven bone

Question 9

Epiphysis:

Answer 9

Distal to growth plate.

Question 10

Metaphysis:

Answer 10

Beneath growth plate

Question 11

Diaphysis:

Answer 11

Center of bone

Question 12

Dysostosis:

Answer 12

• Local* problems in migration of mesenchyme and their condensation.
  
  • Eg. polydactyly/brachydactyly

Question 13

Dysplasia:

Answer 13

Global defect in regulation of skeletal organogenesis

Question 14

Cleidocranial dysplasia (6):

Answer 14

• Autosomal dominant
• RUNX2 transcription factor defect
• Short stature
• Abnormal clavicles
• Supernumerary teeth
• Wormian bone

Question 15

Achondroplasia (4):

Answer 15

• Growth plate defect from paracrine cell defect
• Reduced chondrocyte proliferation in growth plate
• FGFR3 point mutation –> gain of function
• Autosomal dominant

Question 16

Achondroplasia appearance (5):

Answer 16

• Short stature
• Short proximal limbs
• Normal trunk length
• Enlarged head with bulging forehead
• Depression of root of nose

Question 17

Thanatophoric dwarfism (6):

Answer 17

• Most common lethal dwarfism
• Cloverleaf skull
• More severe FGFR3 gain of function mutation
• Micromelic short bowed limbs
• Small underdeveloped chest with bell-shaped abdomen
• Diminished chondrocyte proliferation

Question 18

LRP5 - Gain of function:

Answer 18

Cannot upregulate osteoclasts

- Autosomal dominant osteopetrosis type 1

Question 19

Osteoprorosis pseudoglioma syndrome (3):

Answer 19

• Inactive LRP5
• Skeletal fragility
• Loss of vision

Question 20

Osteopetrosis (5):

Answer 20

• Diffuse systemic bone sclerosis
• Bone deposition replaces medullary cavity
• Bulbous long bones
• Narrow neural foramina
• Brittle bones

Question 21

Osteopetrosis is due to:

Answer 21

Reduced osteoclast bone resorption

- Cannot acidify pit

Question 22

Autosomal dominant benign osteopetrosis (6):

Answer 22

• Adolescent or adulthood
• Multiple fractures
• Mild anemia
• Hepatosplenomegaly
• Mild cranial nerve defects
• Can be treated with bone marrow transplant

Question 23

Osteogenesis imperfecta (4):

Answer 23

• Group of type 1 collagen diseases
• Affects other areas rich in type 1 collagen
• Autosomal dominant
• Fragility vs. child abuse

Question 24

Osteogenesis imperfecta type 1 (5):

Answer 24

• Normal stature with less fractures after puberty
• Blue sclerae from translucency of sclera
• Dentinogenesis imperfecta from dentin defect
• Hearing loss
• Joint laxity

Question 25

Mucopolysaccharidoses (3):

Answer 25

- Defect in enzymes degrading dermatan sulfate, heparan sulfate and keratan sulfate - Abnormalities of hyaline cartilage - Malformed bones

Question 26

Osteoporosis:

Answer 26

Increased bone porosity and decreased mass

Question 27

Aging causes of osteoporosis (4):

Answer 27

- Decreased replicative activity of osteoprogenitor cells - Decreased synthetic activity of osteoblasts - Decreased biologic activity of matrix-bound growth factors - Reduced physical activity

Question 28

Menopausal causes of osteoporosis (4):

Answer 28

- Decreased serum estrogen - Increased cytokines - Increased expression of RANK, RANKL - Increased osteoclast activity

Question 29

Low turnover variant of osteoporosis:

Answer 29

Senile osteoporosis

Question 30

High turnover variant of osteoporosis:

Answer 30

Post-menopausal osteoporosis

Question 31

Secondary osteoporosis (3):

Answer 31

- Hyperparathyroidism - Corticosteroids - Immobilization

Question 32

Brown tumor (3):

Answer 32

- Bone loss due to hyperparathyroidism replaced by fibrovascular tissue - Microfractures result in hemorrhage and healing - Granulation tissue and hemosiderin

Question 33

Paget disease of bone stages (3):

Answer 33

- Osteolytic stage: osteoclast activity - V-shaped lesion - Mixed stage: osteolytic and osteoblastic - Osteosclerotic stage: Mosaic pattern of lamellar bone due to osteoblasts

Question 34

Paget disease labs (2):

Answer 34

- Increased alkaline phosphatase | - Normal calcium and PO4

Question 35

Paget disease: bone overgrowth can lead to (4):

Answer 35

- Cranial nerve palsy - Heavy skull - Severe secondary osteoarthritis - Chalk stick-type fracture

Question 36

Fracture - soft tissue callus (4):

Answer 36

- Hematoma fibrin creates framework - Influx inflammation, fibroblasts and capillaries - Osteoprogenitor cells activated - No rigidity, easily disrupted

Question 37

Fracture - boney callus (4):

Answer 37

- Woven bone - +/- cartilage for enchondral ossification - Maximum girth of callus 3 wks - Over time remodels to bear full weight

Question 38

Osteonecrosis (3):

Answer 38

Avascular necrosis - Infarction of bone and marrow - Corticosteroids most common cause - Dead bone/fat replaced by Ca++ salts

Question 39

Causes of avascular necrosis (6):

Answer 39

- Idiopathic - Corticosteroids - Infection - Dysbarism - Pregnancy - Sickle cell disease

Question 40

Subchondral infarct (2):

Answer 40

- Chronic pain | - Wedge-shaped subchondral bone

Question 41

Osteomyelitis:

Answer 41

Bone inflammation almost always from infection

Question 42

Location of pyogenic osteomyelitis by age (3):

Answer 42

- Neonate: metaphysis and/or epiphysis - Children: metaphysis - Adult: epiphyses and subchondral bone

Question 43

Sequestrum:

Answer 43

Dead piece of bone

Question 44

Brodie Abscess:

Answer 44

Small intraosseous abscess often in the cortex walled off by reactive bone

Question 45

Involucrum:

Answer 45

Reactive surrounding bone

Question 46

Potts disease:

Answer 46

TB infection of spine