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Rheum Lectures > Congenital and Acquired Diseases of Bone Development > Flashcards

Congenital and Acquired Diseases of Bone Development Flashcards

1
Q

What is the organic part of bone made of? and what is its function?

A

Collagen; structure

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2
Q

What is the inorganic part of bone made of? and what is its function?

A

Calcium hydroxyapatite; strength and hardness

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3
Q

What is Osteoid?

A

Bone that is not mineralized

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4
Q

What are the active cell types in bones?

A

Osteoprogenitor, Osteoblasts, Osteoclasts, Osteocytes

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5
Q

What are osteoprogenitor cells?

A

They are pluripotential mesenchymal stem cells that can become osteoblast under CBFA-1 stimulation

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6
Q

What do osteoblasts do?

A

Form Bone

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7
Q

What do osteoclasts do?

A

Remodel Bone

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8
Q

What do osteocytes do?

A

Sense mechanical stress and regulate serum calcium and phophates

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9
Q

What do osteoblasts synthesize?

A

Osteoid

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10
Q

What does osteoid synthesize and what is it a component of?

A

Type 1 Collagen; 90% of organic part

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11
Q

What role do osteoblasts play in regard to osteocytes?

A

They mediate osteoclast activity via PTH receptors located only on osteoblasts

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12
Q

How do osteocytes that are encased in bone communicate?

A

Through cancaliculi

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13
Q

What cytokines are required for osteocyte differentiation?

A

IL-1, IL-3, IL-6, IL-11, GM-CSF, M-CSF

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14
Q

Where do osteocytes reside?

A

Resorption pits; Howship lacunae

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15
Q

Are osteocytes multinucleated?

A

Yes

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16
Q

What stem cells are osteoclasts derived from?

A

Monocytes; the same as macrophages

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17
Q

What signals must the osteoclast precursor receive from the osteoblast to differentiate into a osteoclast?

A

RANK and M-CSF

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18
Q

What can block the RANK-RANK ligand interaction? What does this mean?

A

Osteoprotegerin (OPG) secreted by the Stromal cell; this means OPG prevents bone resorption by inhibiting osteoclast differentiation

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19
Q

What are the diaphysis, metaphysis, and epiphysis of long bones?

A

D: Central portion
M: between diaphysis and epiphysis
E: end of long bones; contains growth plate

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20
Q

Where is blood supplied to in growing bones?

A

The epiphysis

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21
Q

Why are children more prone to osteomyelitis than adults?

A

Richer blood supply in adults

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22
Q

If a part of bone is going to lose circulation, what part is most likely?

A

The end of the bone, cartilage plate

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23
Q

What is osteogenesis imperfecta?

A

It is brittle bone disease due to mutations in T1 collagen genes leading to abnormal skeleton, ligament, skin, sclera, and dentin formation

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24
Q

What is T1 OI?

A

Make little to no pro-alpha1, normal stature, lax joints, and hard of hearing

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25
Q

What is T2 OI?

A

Pro-alpha1 is too short = collagen made but degraded intracellularly = break bones in utero; death in a child

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26
Q

What is T3 OI?

A

Triple helix doesnt form well; lots of short fractures, progressive kyphosis, hard of hearing, bad cases lethal in childhood

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27
Q

What is T4 OI?

A

Pro-alpha2 is too short; short stature, somewhat fragile bones

28
Q

What is the inheritance pattern of OI?

A

Most are AD; type 2’s are either AR or new AD mutations; teeth deformed in moth cases

29
Q

Why are the ribs “beaded” on radiograph of a fetus with OI?

A

Multiple fractures

30
Q

What are the 4 major criteria of OI?

A

Osteoporosis, blue sclerae, dentingenesis imperfecta, premature otosclerosis (2 needed for dx)

31
Q

Why are the sclerae blue in OI?

A

Sclerae are also made up of T1 collagen, therefore thinning of the sclerae makes the underlying choroid visible; this is also seen in pseudocanthoma elasticum, Ehlers-Danlons, and Marfan

32
Q

What is achondroplasia?

A

Reduction in chondrocytes at growth plates, MCC of inherited dwarfism (AD), characterized by short extremities, normal trunk, large head, normal mentation

33
Q

Are muscles, sexuality, and intelligence all normal for achondroplasia?

A

Yes, they may actually be slightly more intelligent

34
Q

What is locus for achondroplasia?

A

Receptor for FGF3

35
Q

What is the risk factor for new mutations for achondroplasia?

A

Advanced paternal age

36
Q

What is the major risk for achondroplasia?

A

Deformity of the foramen magnum, where minor trauma can dislocate the skull and compress brainstem - RARE

37
Q

What is osteopetrosis?

A

It is “Marble bone disease”/stone-like bones due to osteoclast dysfunction

38
Q

What is one variant of osteoclast dysfunction mentioned?

A

Carbonic Anhydrase II deficiency; without CA2 it is impossible to form the acidic environment that is required for resorption = too much osteoblast activity

39
Q

What is the consequence of insufficient osteoclast function?

A

Bones lack medullary canal and are very thick and “chalk” like meaning they are thick but break easily; ends of bone are misshapen and bulbous.

40
Q

On top of brittle and thick bones, what else will patients with osteopetrosis usually have? (in regards to their blood)

A

They are neutropenic and anemic b/c the bone crowds the marrow space

41
Q

What is the most severe form of Osteopetrosis?

A

The malignant, infantile, autosomal recessive variant (ARO)

42
Q

Will there be increased, decreased or a normal amount of osteoclasts in ARO?

A

Normal or elevated; pointing to a dysfunction in their functional capacity, not formation

43
Q

How do you treat these patients?

A

Provide them with osteoclast precursors via bone marrow transplant

44
Q

What is characteristic of bones for osteopetrosis patients (on x-ray)

A

Sclerotic and bulbous ends

45
Q

If there is a loss-of-function mutation of RANK-L, recruitment and activation of osteoclasts doesnt occur properly, what type of osteopetrosis will this result in?

A

Very low number of osteoclasts

46
Q

What is osteoporosis?

A

It is a systemic skeletal disease characterized by low bone mass and micro architectural deterioration of bone tissue leading to enhanced bone fragility and a consequent increase in fracture risk

47
Q

What are the common sites of fracture for osteoporosis?

A

Wrist, hip, and spine

48
Q

What are some major risk factors for osteoporosis?

A

Any of the following: age > 70, menopause < 45, hypogonadism, fragility fracture, malabsorption, immobilization, hip fracture in parents etc, etc, etc

49
Q

What are the 3 major determinants of peak bone mass, when does that occur?

A

Genetics, physical activity, and nutrition peaking in the mid 20’s

50
Q

What role does menopause play in osteoporosis?

A

Decreased serum estrogen leads to increased IL-1, IL_6, and TNF levels, increased expression of RANK and RANKL = increased osteoclast activity

51
Q

What role does age play in osteoporosis?

A

Decreased replicative activity of osteoprogenitor cells, decreased synthetic ability of osteoblasts, decreased biologic activity of matrix bound growh factors, and reduced physical activity

52
Q

The mortality rate of osteoporosis is, in general, dependent on what?

A

The age when hip fracture occurs

53
Q

What is paget disease of bone?

A

An imbalance between excessive osteoclast and osteoblast function; increased bone turnover

54
Q

What are the 4 phases of paget disease of bone?

A

Osteolytic, mixed osteolytic-osteoblastic, osteoblastic and burnt-out stage

55
Q

What are the key clinical points in paget disease?

A

Thick skull, deafness, kyphosis, pain, and bowed legs

56
Q

What predominates in the sclerotic phase of paget disease?

A

irregular lamellar bone

57
Q

What is osteomalacia due to?

A

Failure of bone to mineralize properly in an adult; dietary calcium deficiency or malabsorption

58
Q

What is inadequate vitamin D or calcium in children called?

A

Rickets

59
Q

For osteomalacia/rickets what stain is used and what does it show?

A

von Kossa stain shows calcified tissue as black

60
Q

Renal osteodystrophy is due to?

A

Deficiency of 1,25(OH)2D due to tubular injury = hypocalcemia

61
Q

What is the primary cause of hyperparathyroidism?

A

Adenoma

62
Q

What is the secondary cause of hyperparathyroidism?

A

Prolonged hypoclacemia with compensatory hypersecretion (renal dz)

63
Q

What is the result of either cause of hyperparathyroidism?

A

Unabated PTH secretion = release of mediateors that stimulate osteoclasts and bone resorption

64
Q

What is a brown tumor?

A

Microfracture and hemorrhage; hemosiderin deposition; fibrosis; NOT a neoplasm; focus of increased osteoclast activity; expansile and spongy

65
Q

What is osteitis fibrosa cystica?

A

Extension of brown tumor; pretty much a bunch of cysts brown tumors and hemorrhagic cysts

Rheum Lectures (7 decks)

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