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My Pathoma Unit 5 > Chapter 18 Skeletal System, Bone Tumors, Soft Tissue Tumors > Flashcards

Chapter 18 Skeletal System, Bone Tumors, Soft Tissue Tumors Flashcards

1
Q

What defect is apparent in Achondroplasia? What is it a common cause of?

A

Impaired cartilage proliferation in the growth plate; common cause of dwarfism

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2
Q

What is Achondroplasia due to? and what is the inheritance pattern?

A

Due to an activating mutation in fibroblast growth factor receptor 3 (FGFR3); AD

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3
Q

What does overexpression of FGFR3 cause?

A

Inhibits growth of cartilage

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4
Q

Are most mutations in achondroplasia sporadic or inherited and what are they related to?

A

most are sporadic and related to increased paternal age

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5
Q

What are the clinical features of achondroplasia?

A

Short extremities with normal sized head and chest- due to poor endochondral bone formation; intremembranous bone formation is not affected

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6
Q

Describe Endochondral bone formation? What type of bones are formed this way?

A

Is characterized by formation of a cartilage matrix, which is then replaced by bone; it is the mechanism by which long bones grow. Starts with cartilage matrix, cartilage dies and gets calcified and mineralized into bone.

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7
Q

Describe Intramembranous bone formation?

A

is characterized by formation of bone without a preexisting cartilage matrix; it is the mechanism by which flat bones (skull, ribs, wrist) develop. Produced from a connective tissue matrix

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8
Q

Describe the effect of achondroplasia on mental function, life span, and fertility?

A

Not affected

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9
Q

What defect is apparent in Osteogenesis Imperfecta?

A

Congenital defect of bone formation resulting in structurally weak bone

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10
Q

What is OI most commonly due to? what is the inheritance pattern?

A

Due to an AD defect in collagen type 1 synthesis (type found in bONE)

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11
Q

What are 3 clinical features of OI?

A

1 Multiple fractures of bone (can mimic child abuse, but bruising is absent)
2 Blue Sclera - Thinning of scleral collagen reveals underlying choroidal veins
3 Hearing loss - bones of the middle ear easily fracture

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12
Q

What defect is apparent in Osteopetrosis?

A

Inherited defect of bone resorprtion resulting in abnormally thick, heavy bone that fractures easily.

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13
Q

What is osteopetrosis due to?

A

Due to poor osteoclast function

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14
Q

Multiple genetic variants of osteopetrosis exist, what is the most common?

A

Carbonic anhydrase II mutation leads to loss of the acidic microenvironment required for bone resorption

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15
Q

What are 5 clinical features of osteopetrosis?

A

1 bone fractures
2 pancytopenia with extramedullary hematopoeisis due to bony replacement of the marrow (myelophthisic process)
3 Vision and hearing impairment - due to impingement on cranial nerves
4 hydrocephalus due to narrowing of the foramen magnum
5 Renal tubular acidosis - seen with CAII mutation (lack of CA results in decreased tubular resorption of HCO3 leading to metabolic acidosis

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16
Q

What is the treatment for osteopetrosis?

A

Treatment is bone marrow transplant; osteoclasts are derived from monocytes which come from hematopoiesis

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17
Q

What defect is apparent in Rickets and Osteomalacia?

A

Defective mineralization of osteoid and abnormal deposition of osteoid

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18
Q

What is osteoid and what cell produces it?

A

Osteoblasts normally produce osteoid, which is then mineralized with calcium and phosphate to form bone

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19
Q

What is Rickets/Osteomalacia due to?

A

Due to low levels of vitamin D, which results in low serum calcium and phosphate

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20
Q

What are the two normal sources of vitamin D?

A

Normally derived from the skin upon exposure to sunlight (85%) and from the diet (15%)

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21
Q

What does activation of vitamin D involve?

A

25-hydroxylation by the liver followed by 1 hydroxylation by the proximal tubule cells of the kidney

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22
Q

How does active vitamin D raise serum calcium and phosphate?

A

1 Intestine - increases absorption of calcium and phosphate
2 Kidney - increases reabsorption of calcium and phosphate
3 Bone - increases resorption of calcium and phosphate

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23
Q

What scenarios is vitamin D deficiency seen?

A

decreased sun exposure, poor diet, malabsorption, liver failure, and renal failure

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24
Q

What is rickets due to and what does it cause?

A

Rickets is due to low vitamin D in children, resulting in abnormal bone mineralization

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25
Q

What demographic does rickets most commonly present in?

A

Most commonly arises in children <1 year old

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26
Q

How does rickets present? (4)

A

1 Pigeon breast deformity - inward bending of the ribs with anterior protrusion of the sternum
2 Frontal bossing (enlarged forehead) - due to osteoid deposition on the skull
3 Rachitic rosary - due to osteoid deposition at the costochondral junction
4 Bowing of the legs may be seen in ambulating children

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27
Q

What is Osteomalacia due to?

A

Low vitamin D in adults

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28
Q

What does low vitD in osteomalacia lead to?

A

Inadequate mineralization results in weak bone with an increased risk for fracture in weight bearing bones

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29
Q

What laboratory findings are seen in osteomalacia? Serum calcium, serum phosphate, PTH, Alkaline phosphatase

A

decreased calcium and phosphate

increase PTH and alkaline phosphatase

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30
Q

What is osteoporosis and what does it result in?

A

Reduction in trabecular bone mass, results in porous bone with an increased risk for fracture

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31
Q

What is risk of osteoporosis dependent on?

A

Peak bone mass (attained in early adulthood) and rate of bone loss thereafter

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32
Q

When is peak bone mass achieved and what is it dependent on?

A

Achieved by 30 years of age and based on;
1 genetics (VitD receptor)
2 Diet
3 Exercise

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33
Q

How fast is bone lost after peak bone mass is achieved and what is this rate based on?

A

Lost at lightly less than 1% of bone mass per year and is based on exercise, diet, and estrogen

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34
Q

What are the 2 most common forms of osteoporosis?

A

Senile and postmenopausal

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35
Q

What are the clinical features of osteoporosis and the lab values seen for calcium, phosphate, PTH, alkaline phosphatase

A

1 Bone pain and fractures in weight bearing areas such as the vertebrae (leads to loss of height and kyphosis), hip, and distal radius
2 Serum calcium, phosphate, PTH and alkaline phosphatase are normal

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36
Q

How is bone density measured?

A

DEXA scan

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37
Q

How can Osteomalacia and Osteoporosis be differentiated?

A

By lab values.

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38
Q

What does treatment of osteoporosis involve? (4)

A

1 Exercise, Vitamin D, and calcium - limit bone loss
2 Bisphosphonates - induce apoptosis of osteoclasts
3 Estrogen replacement therapy is debated (Currently not recommended)
4 Glucocorticoids are contraindicated (worsen osteoporosis)

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39
Q

What defect is seen in Paget Disease of Bone?

A

Imbalance between osteoclast and osteoblast function

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40
Q

Who is paget disease of bone normally seen in?

A

usually seen in late adulthood (Average age >60)

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41
Q

What normally controls the function of osteoclasts and what happens in paget disease?

A

Osteoblasts normally manage osteoclasts, in paget disease the osteoclasts go off on their own

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42
Q

What is the etiology of paget disease?

A

etiology is unknown, possibly viral (infection of osteoclasts)

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43
Q

Describe the bone involvement of paget disease?

A

Localized process involving one or more bones; doe snot involve the entire skeleton

44
Q

What are the 3 distinct stages of paget disease?

A

1 osteoclastic
2 mixed osteoclastic/osteoblastic
3 osteoblastic

45
Q

What is the end result of the three stages of paget disease and what does biopsy show?

A

End result is thick, sclerotic bone that fractures easily. Biopsy revelas a mosaic pattern of lamellar bone

46
Q

What are 5 clinical features of paget disease?

A

1 Bone pain - due to microfractures
2 increasing hat size - skull is commonly affected
3 Hearing loss- impingement on cranial nerve
4 Lion-like facies
5 isolated elevated alkaline phosphatase - most common cause of isolated elevated alkaline phosphatase in patients >40 years old

47
Q

What effects does paget disease have on serum calcium, phosphate, and PTH?

A

All are normal

48
Q

What does treatment of Paget disease include?

A

1 calcitonin - inhibits osteoclast function

2 bisphosphonates - induces apoptosis of osteoclasts

49
Q

What doe complications of paget disease include?

A

High output cardiac failure- due to formation of AV shunts in bone
Osteosarcoma

50
Q

What is osteomyelitis?

A

Infection of marrow and bone

51
Q

Is osteomyelitis more common in adults or children?

A

children

52
Q

What is the most common cause of osteomyelitis and how does it reach the bone?

A

Most commonly bacterial; arises via hematogenous spread

53
Q

What etiology and area of long bones is osteomyelitis seen in adults and children?

A

transient bacteremia in children seed metaphysis. Open-wound bacteremia in adults seeds epiphysis

54
Q

What is the most common cause of osteomyelitis?

A

Staph Aureus

55
Q

What is a common cause of osteomyelitis in sexually active adults?

A

N Gonorrhoeae

56
Q

What is a common cause of osteomyelitis in sickle cell disease?

A

Salmonella

57
Q

What is a common cause of osteomyelitis in diabetics or IV drug users?

A

Pseudomonas

58
Q

What is a common cause of osteomyelitis resulting from cat or dog bites?

A

Pasteurella

59
Q

What is a common cause of osteomyelitis in TB patients?

A

Mycobacterium Tuberculosis usually involves vertebrae (pott diesease)

60
Q

What are the clinical features of osteomyelitis? What does it look like on Xray?

A

Bone pain with systemic signs of infection (eg fever and leukocytosis). Lytic focus *Abscess) surrounded by slerosis of bone on x-ray; lytic focus is called sequestrum, and sclerosis is called involucrum

61
Q

How is diagnosis of osteomyelitis made?

A

Blood culture

62
Q

What is avascular necrosis?

A

Ischemic necrosis of bone and bone marrow

63
Q

What do causes of avascular necrosis include?

A

Trauma or fracture (most common), steroids, sick cell anemia (Dactylitis), and caisson disease; gas emboli of N2 precipitates out of the blood and lodges in the bone

64
Q

What are two major complications of avascular necrosis?

A

Osteoarthritis and fracture are major complications

65
Q

What is an osteoma, where does it most commonly arise? and what is it associated with?

A

Benign tumor of bone, most commonly arises on the surface of facial bones, associated with Garner Syndrome

66
Q

What is Gardner syndrome?

A

Familial adenomatous polypopis, Fibromatoiss in the retroperitoneum, and osteomas of facial bones

67
Q

What is fibromatosis?

A

Nonneoplastic growth of fibroblasts that locally destroys tisssue

68
Q

What is an osteoid osteoma?

A

Benign tumor of osteoblasts (that produce osteoid) surrounded by a rim of reactive (sclerotic) bone

69
Q

Who does osteoid osteomas occur in?

A

Occurs in young adults <25 years of age (more common in males)

70
Q

Where does osteoid osteoma arise?

A

Arises in the cortex of long bones (e.g. femur) usually arises on the diaphysis

71
Q

How does osteoid osteoma present?

A

bone pain that resolves with aspirin

72
Q

What does imaging reveal in osteoid osteoma?

A

reveals a bony mass (<2cm) with a radiolucent core (osteoid)

73
Q

What is an osteoblastoma and how does it relate to osteoid osteoma?

A

similar to osteoid osteoma but is larger (>2cm), arises in vertebrae, and presents as bone pain that does not respond to aspirin

74
Q

What is an osteochondroma?

A

Tumor of bone with an overlying cartilage cap; most common benign tumor of bone

75
Q

Where does osteochondroma arise?

A

Arises from a lateral projection of the growth plate (metaphysis); bone is continuous with marrow space

76
Q

What can the overlying cartilage of an osteochomdroma transform into? How common is this transformation?

A

Can transform into a chondrosarcoma. this is rare

77
Q

What is an osteosarcoma?

A

Malignant proliferation of osteoblasts

78
Q

What demographics are peak incidences of osteosarcoma seen in?

A

Teenagers; and less commonly in the elderly

79
Q

What are 3 risk factors of osteosarcoma?

A

familial retinoblastoma, paget disease and radiation (last two in elderly)

80
Q

How does osteosarcoma arise?

A

Arises in the metaphysis of long bones, usually the distal femur or proximal tibia

81
Q

How does osteosarcoma present?

A

Presents as a pathological fracture or bone pain with swelling

82
Q

What does imaging reveal in osteosarcoma?

A

Reveals a destructive mass with a ‘sunburst’ appearing and lifting of the periosteum (Codman triangle)

83
Q

What does biopsu reveal in osteosarcoma?

A

pleomorphic cells that produce osteoid

84
Q

What is Giant Cell Tumor?

A

Tumor comprised of multinucleated giant cells and stromal cells

85
Q

Who does Giant cell tumors occur in?

A

Young adults

86
Q

Where do Giant cell tumors arise?

A

arise on the epiphyis of long bones, usually the distal femur or proximal tibia

87
Q

What appearance is seen on xray in giant cell tumors?

A

‘soap-bubble’ appearance

88
Q

How does a giant cell tumor behave?

A

Locally aggressive tumor; may recur

89
Q

What is a Ewing Sarcoma?

A

Malignant proliferation of poorly differentiated cells derived from neuroectoderm

90
Q

Where does Ewing sarcoma arise and in who?

A

Diaphysis of long bones; usually in male children <15 years old

91
Q

What does biopsy reveal in Ewing sarcoma?

A

small, round blue cells that resemble lymphocytes

92
Q

What can Ewing sarcoma be confused with?

A

Can be confused with lymphoma or chronic osteomyelitis (Some can present with fever)

93
Q

What is the characteristic translocation of Ewing sarcoma?

A

t(11;22)

94
Q

What is a chondroma and where does it arise?

A

Benign tumor of cartilage that usually arises in the medulla of small bones of the hands and feet

95
Q

What is a chondrosarcoma and where does it arise?

A

Malignant cartilage-forming tumor that usually arises in the medulla of the pelvis or central skeleton

96
Q

What is more common in bone, metastatic or primary?

A

metastatic

97
Q

What do bone mets usually result in, what is the one exception?

A

Result in osteolytic (punched out) lesions. The one exception is prostatic carcinoma classically produces osteoblastic lesions (sclerosis)

98
Q

What is a lipoma?

A

Benign tumor of adipose tissue

99
Q

What is the most common benign soft tissue tumor in adults?

A

lipoma

100
Q

What is a liposarcoma and what is the characteristic cell?

A

Malignant tumor of adipose tissue. Lipoblast is the characteristic cell

101
Q

What is the most common malignant soft tissue tumor in adults?

A

liposarcoma

102
Q

What is a rhabdomyoma?

A

Benign tumor of skeletal muscle

103
Q

What is cardiac rhybdomyoma associated with?

A

tuberous sclerosis

104
Q

What is a rhabdomyosarcoma, what is the characteristic cell, and what marker is it positive for?

A

malignant tumor of skeletal muscle. Rhabdomyoblasts are the characteristic cell; desmin positive

105
Q

What are the most common sites for rhyabdomyosarcomas?

A

Head and neck; vagina is the classic site in young girls

106
Q

What is the most common malignant soft tissue tumor in children?

A

rhyabdomyosarcoma

My Pathoma Unit 5 (4 decks)

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