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MSK Week 4 > ICL 1.5: Pathology of Bones > Flashcards

ICL 1.5: Pathology of Bones Flashcards

1
Q

what is the organic matrix of bones mainly made of?

A

type I collagen

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2
Q

what is the inorganic matrix of bone mainly made of?

A

calcium hydroxyapatite

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3
Q

what 2 things regulates bone formation and resolution?

A
  1. RANK and RANKL

they increase osteoclast activity = dissolve bone

  1. osteoprotegerin inhibits osteoclasts = makes new bone
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4
Q

what does woven bone signify in adults?

A

it’s pathologic, something is wrong….

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5
Q

what does woven bone look like?

A

it’s not stress oriented; you don’t see lamellar lines so it’s just random collagen oriented in different directions

a lot more osteocytes in the area

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6
Q

what is dysostoses?

A

defects in mesenchymal migration and condensation

usually focal abnormality; it involves a single bone

ex. supernumerary digits or ribs = extra bones

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7
Q

what is dysplasias?

A

abnormal proliferation or maturation of chondrocytes and osteoblasts or abnormal collagen and noncollagenous proteins

ALL cartilage or bone affected

ex. achondroplasia or osteogenesis imperfecta

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8
Q

what is achondroplasia?

A

impaired maturation of cartilage in the developing growth plate, due to mutation in FGFR3 gene

fibroblast growth factor receptor 3 is constantly active due to mutation – FGFR3 normally inhibits cartilage so if it’s always active then the cartilage can’t grow then your bones can’t elongate

it’s the most common growth plate disease –> it’s a major cause of dwarfism!

80% cases new spontaneous mutation, but if inherited it is autosomal dominant

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9
Q

what is the patient presentation of someone with achondroplasia?

A
  1. normal trunk
  2. shortened limbs
  3. skin piles up because bones aren’t elongating
  4. enlarged head, bulging forehead
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10
Q

what is the most common dysplasia?

A

achondroplasia

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11
Q

what is osteogenesis imperfecta?

A

“brittle bone disease”

it’s an abnormal development of type I collagen which is a major component of osteoid due to defective osteoblasts!!

there’s a spectrum of this disease from mild to lethal

it’s the most common inherited disorder of connective tissue

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12
Q

what is the patient presentation of someone with osteogenesis imperfecta?

A
  1. multiple bone fractures (rule out child abuse)
  2. blue sclera* (due to decreased collagen and blood vessels shine through)
  3. misshapen, blue-yellow teeth
  4. hearing loss due to abnormal middle ear bones
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13
Q

what is the inheritance pattern of achondroplasia?

A

autosomal dominant

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14
Q

what is the inheritance pattern of osteogenesis imperfecta?

A

autosomal dominant

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15
Q

what is osteopetrosis?

A

defective osteoclasts –> carbonic anhydrase deficiency leads to inability of osteoclasts to acidify and dissolve bone

“marble bone disease” = dense bone sclerosis, but brittle, easily fractured and misshapen bones

the medullary cavity filled with spongiosa, NO hematopoiesis –> pancytopenia because they don’t have normal BM so they’ll be anemic and get lots of infections

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16
Q

what does an x-ray of osteopetrosis look like?

A

erlenmeyer flask deformity at the ends of the radius and ulna

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17
Q

what classifies as primary osteoporosis?

A
  1. postmenopausal (female)***
  2. senile (males)
  3. idiopathic
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18
Q

what classifies as secondary osteoporosis?

A
  1. endocrine, e.g. hyperparathyroidism
  2. neoplasia, e.g. multiple myeloma
  3. gastrointestinal
  4. systemic rheumatological diseases
  5. drugs-exogenous glucocorticoids ***
  6. miscellaneous

eh don’t really worry about these

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19
Q

what happens during your bone mass when you’re a kid?

A

normally, bone mass increases in infancy and childhood

so running around outside increases your bone mass

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20
Q

what determines your peak bone mass?

A
  1. genetics (vitamin D receptor)
  2. physical activity = stimulus for bone remodeling
  3. diet (vitamin D and calcium)
  4. age (0.7% bone loss a year)
  5. hormonal status
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21
Q

what happens to the bone mass of post-menopausal women?

A

post-menopausal bone loss 2%/year cortical bone, 9%/year cancellous bone

estrogen influences the development of osteoporosis

decreased estrogen leads to decreased bone mass due to decreased osteoblast activity and increased osteoclast activity

50% of women will have postmenopausal osteoporosis fractures, due to loss of 35-50% of their bone mass!!! (vertebral and hip fractures are common)

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22
Q

what is the morphology of osteoporosis?

A

mainly affects cancellous bone (senile osteoporosis leans to cortical bone loss)

trabeculae become thinner and farther apart

there’s increased susceptibility to fracture

often effects the vertebral bodies and other weight bearing places like the femoral neck

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23
Q

what does a patient with osteoporosis clinically present with?

A

that big hump that women get in their thoracic back because their vertebrae are losing this bone density!!

the vertebra are fracturing and collapsing and the person gets shorter and shorter

“Dowager’s hump”

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24
Q

how do you diagnose osteoporosis?

A

x-ray absorptiometry or CT density

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25
Q

how do you prevent and treat osteoporosis?

A
  1. exercise
  2. calcium and vitamin D intake
  3. estrogen replacement
  4. bisphosphonates
  5. recombinant PTH
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26
Q

what is Paget disease?

A

a disorder characterized by “matrix madness”

the bone doesn’t know what it wants to do –> there’s an osteolytic stage where the bone is dissolving, an osteoblastic stage where the bone is growing and there’s a mixed osteoclastic-osteoblastic stage where it’s just confused and you can see all of these stages in the same bone!!!

end result is increased bone mass but it’s disorganized and architecturally abnormal

affects 5-10% of White Europeans

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27
Q

what is the morphology of Paget disease under the microscope?

A

mosaic pattern (jigsaw puzzle) of lamellar bone is pathognomonic – but we don’t get bone biopsies for this lol it’s done by x-ray

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28
Q

what are the 2 types of Paget disease?

A
  1. monostotic (15%)

only one bone involved; usually tibia, ilium, femur, skull, vertebra, humerus

  1. polyostotic (85%)

pelvis, spine, skull

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29
Q

how do you treat Paget disease?

A

most patients have mild symptoms easily treated with calcitonin and bisphosphonates

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30
Q

what is the patient presentation of Paget disease?

A
  1. lots of metabolic activity means lots of blood vessels will start to go towards that bone and you might fee some warmth in the area along with the hypervascularity
  2. PAIN is the most common complaint from micro fractures
  3. leontiasis ossea = massive heavy skull, hearing loss
  4. bowing of legs, distortion of femoral head
  5. malignancy risk because of the high metabolic activity and lots of cells growing and dividing = increased risk for osteosarcoma**
  6. increased alkaline phosphatase; Ca and PO4 are normal though
31
Q

how do you diagnose Paget disease?

A
  1. patient complaints

2. x-ray

32
Q

what is leontiasis ossea?

A

one of the most severe effects of Paget disease

giant skull with abnormal bone thickening

33
Q

what does vitamin D deficiency cause?

A

low vit. D → hypocalcemia → excess unmineralized bone matrix

it’s called Rickets in kids and osteomalacia in adults

in both diseases, there’s decreased mineralized matrix so the bones won’t support weight (can get leg bowing)

34
Q

what is hyperparathyroidism?

A

the parathyroid secretes PTH which makes you dissolve bones and increases Ca in the blood

with hyperparathyroidism you get the bone disease osteitis fibrous cystic because you’re dissolving so much bone and you’ll get lots of pain and microfractures

loss of bone with microfractures leads to hemorrhage into the bone, with giant cells and fibrosis = “brown tumor”

cortical bone is preferentially affected

35
Q

what is renal osteodystrophy?

A

it describes all skeletal changes associated with chronic renal failure; you see a lot of things

  1. increased osteoclastic bone resorption
  2. delayed matrix mineralization (osteomalacia)
  3. osteosclerosis
  4. growth retardation
  5. osteoporosis
36
Q

why are the bones abnormal in renal kidney disease?

A
  1. when you have renal failure, one

the functions of the kidney is to excrete acid waste products

if you can’t do this, you get acidosis and acid dissolves calcium and bone!

  1. another reason is because the second function is to excrete products like phosphates – so if the kidney can’t excrete phosphate it builds up in the blood and calcium and phosphate go in opposite directions which means calcium is low in the blood

if Ca is low in the blood, the parathyroid gland puts out PTH and you get secondary hyperparathyroidism trying to get the Ca levels up and the end result is breaking down bones because of increased osteoclast activity

37
Q

what is osteonecrosis?

A

aka avascular necrosis = ischemia of the bone and the bone dies from lack of blood flow

commonly happens in the femoral head because it doesn’t have good blood flow in the first place –> this is why a lot of hip replacements are done for avascular necrosis

pain is the most common presentation because of the necrosis

most cases are idiopathic or secondary to steroids

38
Q

what can cause avascular necrosis?

A
  1. mechanical vascular interruption
  2. corticosteroids
  3. thrombosis, sickle cell disease
  4. vessel injury
  5. increased intraosseous pressure with vascular compression
  6. venous hypertension
39
Q

what is the morphology of a bone with avascular necrosis?

A
  1. medullary infarcts involve cancellous bone and marrow

2. subchondral infarcts are wedge-shaped

40
Q

in the world of neoplasms of bone, are metastic lesions or primary bone tumors more common?

A

metastatic lesions&raquo_space;> primary bone tumors

most metastases are osteolytic = tumor cells secrete PTHRH, prostaglandins or interleukins that stimulate osteoclast bone resorption

but some maybe osteoblastic (by stimulation of osteoblasts) –> prostate cancer is the only one that does this

41
Q

what are the most common neoplasms metastasizing to bone?

A
  1. prostate
  2. breast
  3. lung
  4. kidney
  5. GI
  6. thyroid

Kinds Of Tumors Leaping Promptly To Bone

kidney, ovary, testis, lung, prostate, thyroid, breast

42
Q

what is the most common patient age and location for osteosarcoma?

A
  1. most common in teens

2. knee

43
Q

what is the most common patient age and location for chondrosarcoma?

A
  1. adults

2. trunk, limb, girdles, proximal long bones

44
Q

what is the most common location for giant cell tumors?

A

epiphysis of long bones

45
Q

what is the most common location for Ewing sarcomas?

A

diaphysis of the bone

46
Q

during what time period of life are benign tumors more common?

A

first 3 decades of life

malignant tumors are more common in the elderly

47
Q

what are the most common benign tumors of the bone?

A
  1. osteoid osteoma
  2. osteochondroma
  3. chondroma
  4. fibrous cortical defect (non-ossifying fibroma)
  5. fibrous dysplasia
  6. giant cell tumor
  7. Aneurysmal bone cyst
48
Q

what is an osteoid osteoma?

A

benign tumor of the bone common in teenagers

femur or tibia *cortical lesions that are super painful due to prostaglandin E2 being formed by the tumor –> relieved by aspirin

biopsy would show random woven bone rimmed by osteoblasts (woven bone is always pathologic!)

49
Q

what is an osteochondroma?

A

benign tumor of the bone

arise from metaphysic near growth plate of the knee because a lot of growth is happening there

asymptomatic

it’s 1/3 of all benign bone tumors!! really common!!

50
Q

what is the epidemiology of an osteochondroma?

A

most are solitary lesions but there can be multiple in familial hereditary exostosis (rarely become chondrosarcoma)

M>F

most in children and adolescents and around the knee

51
Q

what is the morphology of an osteochondroma?

A

broad base, bony growth AWAY from epiphyseal plate with a hyaline cartilage cap

kind of looks like a mushroom growing off of the bone at the level of the epiphyseal plate with a little cartilage cap

super easy to diagnose with x-ray

52
Q

what is a chondroma?

A

benign tumor involving the cartilage only!

most common in the medullar cavity of the small bones of the fingers or toes

effects 20-50 year olds

a juxtacortical chondroma is specifically on the bone surface

53
Q

what is Ollier disease?

A

multiple enchondromas

54
Q

what is Mafucci syndrome?

A

multiple enchondroma with soft tissue hemangiomas

there’s increased risk of ovarian and brain gliomas

55
Q

what is a fibrous cortical defect?

A

aka non-ossifying fibroma = no bone formation in this tumor! instead you see it’s benign fibroblasts in storiform spoke pattern and histiocytes (giant cells or foamy macrophages)

very common, especially in kids

most lesions are asymptomatic and discovered incidentally in x-rays –> usually around the knee

larger lesions can cause pathologic fractures

most of these just go away by themselves…

56
Q

what are the 3 clinical presentations of fibrous dysplasia?

A
  1. monostotic: single bone lesion, most common*, most are asymptomatic, teenagers, lots of locations (ribs/femur/tibia/jaw/skull/humerus)
  2. Polyostotic: younger patients, craniofacial bones/hip and shoulder girdles resulting in arthritis
  3. Polyostotic disease with café au lait skin lesions and endocrine abnormality, esp. precocious puberty

the more lesions you have the higher your risk for sarcoma but like we said, a single lesion is what’s more common

not a very common type of lesion

57
Q

what is a giant cell tumor of the bone?

A

patients usually 20-40 years of age

mostly around the knee, pain or pathologic fracture

2 cell populations = mononuclear cells and giant cells = single cell vs. multinucleate cell

benign but locally aggressive

only 4% metastasize to lungs

58
Q

what is an aneurysmal bone cyst?

A

multiloculated blood-filled cystic spaces surrounded by a wall of fibroblasts, giant cells and reactive bone

generally seen in patients during their first 2 decades

lesions are most often in metaphysis of long bones

lots of pain and swelling

59
Q

what are the most common malignant tumors of bone?

A
  1. osteosarcoma
  2. chondrosarcoma
  3. fibrosarcoma and malignant fibrous histiocytoma
  4. Ewing sarcoma and primitive neuroextodermal tumor
60
Q

what is an osteosarcoma?

A

a malignant bone tumor –> a malignant mesenchymal neoplasm that produces osteoid

it’s the most common primary malignant tumor of bone exclusive of myeloma and lymphoma

could be secondary due to Paget disease or radiation

usually happens during the second decade of life and effects the distal femur and proximal tibia at the metaphysis (the knee!!)

M > F

61
Q

what’s the pathogenesis of osteosarcoma?

A
  1. genetics

p53 mutation

  1. predisposing conditions

Paget disease or radiation

62
Q

what is the morphology of an osteosarcoma?

A
  1. Metaphysis, around knee
  2. Osteolytic and invades soft tissue
  3. Codman triangle (raised calcified periosteum you can see on x-ray)
  4. formation of bone (osteoid) is characteristic
63
Q

what’s the clinical presentation of an osteosarcoma?

A

enlarge progressively and painful

fractures due to dissolving of cortical bone

metastasize early by hematogenous route, 20% have obvious lung mets at Dx, and most have micro-mets at Dx

secondary osteosarcomas are more aggressive

64
Q

what is a condrosarcoma?

A

neoplastic malignant cartilage tumor

NO bone formation, which would be classified as chondroblastic osteosarcoma

usually effects the pelvis, shoulder and ribs –> patients will have painful enlarging masses in these locations

patients over 40 mostly effected

not very common

65
Q

what is a fibrosarcoma?

A

malignant tumor of fibrous tissue (NO bone formation) –> fibrous tissue produces collagen

large destructive masses, usually metaphysis of long bones and pelvis

effects the middle-age to elderly

some tumors referred to as MFH = malignant fibrous histiocytoma

66
Q

what is an Ewing sarcoma?

A

a family of malignant neoplasms of which Ewing Sarcoma (EWS, undifferentiated) and Primitive Neuroectodermal tumor (PNET, with neural differentiation) account for 6-10% of all primary bone tumors (second most common bone tumors)

tumor variants are united by common neural origin and genetic translocations

patient population most effected is children and adolescents with peak age in second decade

aggressive ):

67
Q

what is the morphology of Ewing sarcoma?

A

soft expansile mass in medullary cavity

sheets of primitive basophilic cells that do not produce osteoid

small round blue cells tumors or maybe Homer-Wright rosettes

usually effects the femur, tibia and pelvis (not really around the knee)

68
Q

what is the translocation associated with all Ewings sarcomas?

A

t(11;22)

EWS gene on 22 fuses most commonly with transcription factor gene FLI1, stimulating cell proliferation

69
Q

Codman’s triangle

A

osteosarcoma

70
Q

painful, aspirin helps

A

osteoid osteoma

71
Q

mushroom shaped

A

osteochondroma

72
Q

Homer Wright rosettes

A

Ewings sarcoma

73
Q

bony “Chinese letters”

A

fibrous dysplasia

MSK Week 4 (11 decks)

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