MSK 424 - 428

Question 1

explain why estrogen is bone protective

Answer 1

estrogen blocks apoptosis in bone forming osteoblast and induces apoptosis in bone-resorbing osteoclast

Question 2

what bone cell secretes acid and collagenases?

Answer 2

osteoclast

Question 3

what cell is multinucleated and is derived from monocyte?

Answer 3

osteoclast

Question 4

what bone path takes place in epiphysis?

Answer 4

Giant cell tumor

Question 5

what bone paths take place in metaphysis?

Answer 5

osteosarcoma, osteochondroma

Question 6

what bone paths take place in diaphysis?

Answer 6

Ewing sarcoma, myeloma, osteoid osteoma

Question 7

which bone path is associated with nighttime pain, central nidus, and pain released by aspirin?

Answer 7

osteoid osteoma

Question 8

3 characteristics of Ewing sarcoma?

Answer 8

1. anaplastic small blue cell malignant tumor
2. extremely aggressive with early metastases, but responsive to chemotherapy
3. “onion skin” periosteal reaction in bone

Question 9

what population is most affected by Ewing sarcoma?

Answer 9

boys

Question 10

what is the 2nd most common primary malignant tumor after multiple myeloma?

Answer 10

osteosarcoma (osteogenic sarcoma)

Question 11

name 5 predisposing factors for osteosarcoma (osteogenic sarcoma)

Answer 11

1. paget dz of bone
2. bone infarcts
3. radiation
4. familial retinoblastoma
5. Li Fraumeni syndrome (germline p53 mutation)

Question 12

what is the age distribution who get osteosarcoma?

Answer 12

biomodal distribution (10-20 yr old and more than 65)

Question 13

what other malignancy has also bimodal distribution?

Answer 13

hodgkin (young adulthood and more than 55)

Question 14

on x-ray, how will osteosarcoma look like?

Answer 14

codman triangle (from elevation of periosteum) or sunburst pattern on x-ray

Question 15

what is the most common benign tumor?

Answer 15

osteochondroma

Question 16

does osteochondroma transform to chondrosarcoma?

Answer 16

rarely yes

Question 17

what is the characteristic of osteochondroma?

Answer 17

mature bone with cartilagionus (chondroid) cap

Question 18

what bone tumor is characterized as soap bubble appearance on x-ray with multinucleated giant cells

Answer 18

giant cell tumor

Question 19

what is the most common site of giant cell tumor?

Answer 19

epiphyseal end of long bone around knee

Question 20

in paget dz of bone, hearing loss is due to

Answer 20

auditory foramen narrowing

Question 21

name the 4 stages of paget dz of bone

Answer 21

1. lytic (osteoclast)
2. mixed (osteoclast + osteoblast)
3. sclerotic (osteoblast)
4. quiescent (minimal osteoclast/osteoblast)

Question 22

explain the pathophysio of the paget dz of bone

Answer 22

common, localized disorder of bone remodeling cause by inc in both osteoblastic and osteoclastic activity

Question 23

what bone path is associated with mosaic pattern of woven and lamellar bone?

Answer 23

paget dz of bone

Question 24

what is the most common site of osteonecrosis (avascular necrosis) and why?

Answer 24

femoral head (due to insufficiency of medial circumflex femoral artery)

Question 25

name 7 causes for osteonecrosis

Answer 25

ASEPTIC 1. alcoholism 2. sickle cell 3. storage dz (Guacher) 4. exogenous steroid 5. pancreatic 6. trauma 7. idiopathic 8. caisson (the bend)

Question 26

what is another name for idiopathic cause of osteonecrosis?

Answer 26

Legg Calve Perthes dz

Question 27

phosphorylation of myosin is done by what enzyme and will this lead to contraction or relaxation?

Answer 27

myosin light chain kinase, contraction

Question 28

dephosphorylation of myosin is done by what enzyme and what will this lead to?

Answer 28

myosin light chain phosphatase, relaxation

Question 29

inc Ca2+ calmodulin complex activates which enzyme?

Answer 29

myosin light chain kinase

Question 30

bones of axial and appendicular skeleton and base of skull are considered as what type of bone formation?

Answer 30

endochondral ossification

Question 31

what is membranous ossification?

Answer 31

bones of calvarium and facial bones

Question 32

woven bone is formed directly without

Answer 32

cartilage

Question 33

cartilaginous model of bone is first made by

Answer 33

chondrocytes

Question 34

what is the pathophysio of achondroplasia?

Answer 34

(gain of function), constitutive activation of fibroblast growth factor receptor (FGFR3) inhibiting chondrocyte proliferation

Question 35

mode of inheritance of achondroplasia?

Answer 35

autosomal dominant with full penetrance (homozygosity is lethal)

Question 36

how is Laron syndrome diff from achondroplasia?

Answer 36

small genitalia, dec linear growth, everything small due to defective growth hormone receptor

Question 37

treatment drugs for type 2 (senile) osteoporosis?

Answer 37

bisphosphonate, PTH analog (teriparatide), SERMs, calcitonin, denosumab

Question 38

what is denosumab?

Answer 38

monoclonal antibody against RANKL

Question 39

what bone path is associated with bone filling marrow space leading to pancytopenia and extramedullary hematopoiesis?

Answer 39

osteopetrosis (marble bone dz)

Question 40

what is defective in osteopetrosis?

Answer 40

failure of normal bone resorption due to defective osteoclast leading to thickened, dense bones that are prone to fracture

Question 41

what mutation is responsible for osteopetrosis?

Answer 41

mutations in carbonic anhydrase II impairing the ability of osteoclast to generate acidic environment necessary for bone resorption

Question 42

what renal path will also have impaired carbonic anhydrase?

Answer 42

proximal (type2) urine pH

Question 43

what is the treatment for osteopetrosis?

Answer 43

bone marrow transplant is curative as osteoclast is from monocytes

Question 44

what path is associated with "bone-in-bone" appearance on x-ray?

Answer 44

osteopetrosis

Question 45

what is the diff btw osteoporosis and osteomalacia in terms of bone mineralization?

Answer 45

normal bone mineralization in osteoporosis abnormal bone minerailization in osteomalacia (rickets)

Question 46

4 causes for primary osteoporosis?

Answer 46

1. long term steroid use 2. anticonvulsant 3. anticoagulants 4. thyroid replacement therapy

Question 47

what symptoms/fractures can you get from osteoporosis?

Answer 47

1. vertebral compression fractures associated with acute back pain, loss of height, kyphosis 2. fractures of femoral neck 3. fractures of distal radius (Colles fractures)

Question 48

2 bone paths with normal lab values?

Answer 48

1. osteoporosis | 2. osteopetrosis

Question 49

what two bone paths will have the opposite lab values (Ca2+, PO43-, PTH, except for ALP)?

Answer 49

osteomalacia/rickets and hypervitaminosis

Question 50

2 causes for hypervitaminosis?

Answer 50

1. oversupplementation | 2. granulomatous dz (sarcoidosis)

Question 51

explain how the lab values will be diff btw 1' hyperparathyroidism vs 2'

Answer 51

1': high PTH --> high Ca2+ --> low PO43-, high ALP 2': high PO43- --> low Ca2+ --> high PTH, high ALP

Question 52

in 2' hyperparathyroidism, what causes high PO43- conc?

Answer 52

usually due to dec PO43- from ESRD

Question 53

in 2' hyperparathyroidism, what causes low serum Ca2+?

Answer 53

due to low activated vit D due to ESRD