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Specialty Medicine > Genetic & Metabolic Bone Disorders > Flashcards

Genetic & Metabolic Bone Disorders Flashcards

1
Q

What are the two general components of bone?

A

Organic and inorganic

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2
Q

What are the components of the organic component of bone?

A

Cells and matrix proteins

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3
Q

What are the cells that are in the organic part of bone? (4)

A

Osteoprogenitor cells
Osteoblasts
Osteocytes
Osteoclasts

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4
Q

What are the components of the matrix in organic bone?

A

Collagen type I

Non-collagenous proteins

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5
Q

What is the main component of inorganic bone?

A

calcium hydroxyapatite

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6
Q

What is unmineralized bone called?

A

Osteoid

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7
Q

What are osteoprogenitor cells?

A

Pluripotential mesenchymal cells that can form osteoblasts

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8
Q

What is the function of osteoblasts?

A

Synthesize and transport protein and osteoprotegerin, and initiate mineralization

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9
Q

What is the function of the RANK-L protein?

A

receptor on osteoblasts that binds to RANK receptor on osteoclasts to stimulate osteoclastic bone resorption

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10
Q

What is the precursor cell to osteoclasts?

A

Hematopoietic progenitor cells (fused monocytes/ Macrophages)

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11
Q

What is the role of osteoprotegerin?

A

Decoy receptor for RANKL, to prevent osteoclast activation

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12
Q

What are osteocytes? What is their function?

A
  • Osteoblasts that have become surrounded by matrix

- Regulate daily serum Ca levels

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13
Q

How do osteoclasts appear histologically?

A

Multiple nuclei

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14
Q

Where is osteoprotegerin found?

A

Osteoclasts

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15
Q

How do osteocytes communicate with one another?

A

canaliculi

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16
Q

What is osteoid?

A

Unmineralized organic matrix that is lined by osteoblasts

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17
Q

What are the lacunae in which osteoclasts reside?

A

Howship lacunae

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18
Q

What part of the bone do osteoclasts not resorb?

A

Bone lined by osteoid or unmineralized cartilage

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19
Q

What is woven bone and laminar bone?

A

Woven bone = Collagen deposited in a random arrangement

Lamellar bone = bone deposited in an orderly, parallel arrangement

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20
Q

Where is woven bone usually present?

A

Fetal skeleton, at the growth plates, and in processes where there is very rapid bone production

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21
Q

True or false: Woven bone is almost always pathologic in adults

A

True

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22
Q

Where is lamellar bone located?

A

Only type of bone in adults

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23
Q

What are the 4 types of lamellar bone?

A
  • Concentric
  • Interstitial
  • Inner circumferential
  • Outer circumferential
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24
Q

Which is more sturdy–lamellar bone or woven bone?

A

Lamellar bone

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25
Q

What type of bone comprises calluses?

A

Woven bone

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26
Q

What are the causes of woven bone deposition in adults?

A
  • calluses
  • Fibrous dysplasia
  • Areas surrounding tumors or infection
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27
Q

Which has more osteocytes: woven or lamellar bone?

A

Lamellar bone

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28
Q

What is an osteon?

A

Haversian canal + surrounding circular lamellar bone

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29
Q

What lines woven bone?

A

Osteoblasts

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30
Q

What are type I - IV of collagen?

A 
I = bone
II = cartilage
III = reticular
IV = BM
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31
Q

What, generally, is achondroplasia?

A

Fusion of the epiphyseal plates before full maturity

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32
Q

What is the genetic cause of achondroplasia?

A

Reduction in the proliferation of chondrocytes in developing growth plates d/t pt mutation in FGFR3

33
Q

What is the normal role of FGFR3?

A

Inhibition of normal proliferation of chondrocytes at the growth plate (this is constitutively active in achondroplasia)

34
Q

True or false: achondroplasia is usually inherited

A

false–most are sporadic mutations

35
Q

If achondroplasia is inherited, what inheritance pattern does it follow?

A

AD

36
Q

True or false: homozygotes for FGFR3 mutation is lethal

A

True–Small chest wall = respiratory failure

37
Q

What happens to the ones of proliferation in achondroplasia?

A

hypertrophied, narrowed, and disorganized

38
Q

Which bones are usually short in achondroplasia?

A

All bones from formed cartilage

39
Q

True or false: mental and reproductive development in achondroplasia is usually normal

A

True

40
Q

What happens to the trunk with achondroplasia?

A

Normal length

41
Q

What are the five zones of normal epiphyseal plate growth?

A
  1. Reserve zone
  2. proliferation
  3. hypertrophy
  4. Mineralization
  5. Spongiosa
42
Q

What happens to the zones of epiphyseal plates with achondroplasia?

A

Disorganization with transverse bars of bone sealing of plate growth

43
Q

How is the head relative to the rest of the body with achondroplasia?

A

Enlarged with frontal bossing

44
Q

What is the defect with osteogenesis imperfecta?

A

Abnormalities of type I collagen synthesis results in extreme bone fragility and thinning of bone cortex and trabeculae

45
Q

What is the genetic cause of osteogenesis imperfecta, and what is the inheritance pattern?

A

Mutations in alpha 1 and 2 collagen chains

AD

46
Q

What is type I OI?

A

increased risk of fracture, but is usually not deforming

47
Q

What is type II OI?

A

Lethal–multiple fractures in utero with fetal demise

48
Q

What is OI type III and IV?

A

Progressive deformities

49
Q

What happens to the bone with OI?

A

Thinning of the cortex and trabeculae, with reduced numbers of trabeculae

50
Q

What are the eye findings with OI?

A

Blue sclerae

51
Q

What are the dental findings of patients with OI?

A

Amber, yellowish brown or translucent

52
Q

What may happen to hearing with OI?

A

Decreased

53
Q

True or false: patients with OI have a normal survival rate

A

True

54
Q

What happens to the bones in type III and IV OI?

A

Bowing and breaking

55
Q

What is osteopetrosis?

A

Marble bone disease–group of genetic diseases caused by decreased osteoclastic bone resorption, leading to diffuse skeletal sclerosis

56
Q

What is the inheritance pattern of Osteopetrosis?

A

AR malignant

AD benign

57
Q

What is the major cellular issue with osteopetrosis?

A

Defective osteoclastic activity, leading to abnormally thickened, heavily mineralized, and brittle bone

58
Q

What causes the hematological abnormalities with osteopetrosis?

A

Encroachment on the bone marrow leads to reduced cellular proliferation

59
Q

What are the features of the clinical presentation of osteopetrosis?

A
  • Anemia/ thrombocytopenia
  • Increased fractures
  • CN palsies from compression
  • Increased infx susceptibility
60
Q

What is the role of bone marrow transplant with osteopetrosis?

A

helpful–provides progenitor cells which produce normal osteoclasts, which can reverse many of the skeletal abnormalities

61
Q

What are the primary causes of osteoporosis?

A

Menopause

Age

62
Q

What are the common secondary causes of osteoporosis?

A

Glucocorticoid induced

Immobilization induced

63
Q

What, generally, is the pathophysiology of osteoporosis?

A

Reduction of bone mass

64
Q

What are the histological findings of osteoporosis?

A
  • Cortex and trabeculae are thinned, but remain of normal composition
  • Increase porosity of the bone
65
Q

By the time you’re able to diagnose osteoporosis be x-ray, what percent of bone is lost?

A

40%

66
Q

What bones are particularly affected with osteoporosis?

A

Trabecular bone, such as, weight bearing bones

67
Q

what is the role of estrogen in preventing bone formation?

A
  • Increased production of osteoprotegerin

- Increase in collagen synthesis by osteoblasts

68
Q

What happens when estrogen levels fall with bone formation?

A
  • Increased production of RANKL

- Decreased osteoprotegerin

69
Q

What are wedge fractures?

A

When the anterior column of the vertebral body is compressed, leading to kyphosis, but usually with preservation of the spinal cord

70
Q

What are burst fractures?

A

Axial load disrupts the anterior, middle, and/or posterior columns, frequently leading to disruption of the spinal cord

71
Q

What happens to the vertebral bodies with osteoporosis?

A

Shorten

72
Q

How do glucocorticoids cause osteoporosis? (3)

A

Increase in osteoclast survival, decrease in osteoblastogenesis, and increased apoptosis of osteocytes

73
Q

What causes rickets and osteomalacia?

A

Defective mineralization caused by vit D deficiency

74
Q

What is the effect of rickets in children?

A

heaping of unmineralized matrix leads to softening of bones and increased fractures

75
Q

What are the causes of Vit D deficiency in the developed world?

A

malabsorption syndromes

Liver/kidney disease

76
Q

What are the s/sx of osteomalacia?

A
  • generalized pain
  • fractures
  • Mottled areas of bone lucency
77
Q

What are the s/sx of rickets?

A
  • bowing of the legs
  • Frontal bossing
  • Pectus carinatum
78
Q

What is the Rachitic rosary? What causes it?

A
  • The prominent knobs of bone at the costochondral joints of rickets patients
  • Bones grow in thickness, but not length
79
Q

What happens histologically with osteomalacia?

A

More osteoid, causing a more malleable bone

Specialty Medicine (36 decks)

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