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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
What is T2 OI?
Pro-alpha1 is too short = collagen made but degraded intracellularly = break bones in utero; death in a child
26
What is T3 OI?
Triple helix doesnt form well; lots of short fractures, progressive kyphosis, hard of hearing, bad cases lethal in childhood
27
What is T4 OI?
Pro-alpha2 is too short; short stature, somewhat fragile bones
28
What is the inheritance pattern of OI?
Most are AD; type 2's are either AR or new AD mutations; teeth deformed in moth cases
29
Why are the ribs "beaded" on radiograph of a fetus with OI?
Multiple fractures
30
What are the 4 major criteria of OI?
Osteoporosis, blue sclerae, dentingenesis imperfecta, premature otosclerosis (2 needed for dx)
31
Why are the sclerae blue in OI?
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
What is achondroplasia?
Reduction in chondrocytes at growth plates, MCC of inherited dwarfism (AD), characterized by short extremities, normal trunk, large head, normal mentation
33
Are muscles, sexuality, and intelligence all normal for achondroplasia?
Yes, they may actually be slightly more intelligent
34
What is locus for achondroplasia?
Receptor for FGF3
35
What is the risk factor for new mutations for achondroplasia?
Advanced paternal age
36
What is the major risk for achondroplasia?
Deformity of the foramen magnum, where minor trauma can dislocate the skull and compress brainstem - RARE
37
What is osteopetrosis?
It is "Marble bone disease"/stone-like bones due to osteoclast dysfunction
38
What is one variant of osteoclast dysfunction mentioned?
Carbonic Anhydrase II deficiency; without CA2 it is impossible to form the acidic environment that is required for resorption = too much osteoblast activity
39
What is the consequence of insufficient osteoclast function?
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
On top of brittle and thick bones, what else will patients with osteopetrosis usually have? (in regards to their blood)
They are neutropenic and anemic b/c the bone crowds the marrow space
41
What is the most severe form of Osteopetrosis?
The malignant, infantile, autosomal recessive variant (ARO)
42
Will there be increased, decreased or a normal amount of osteoclasts in ARO?
Normal or elevated; pointing to a dysfunction in their functional capacity, not formation
43
How do you treat these patients?
Provide them with osteoclast precursors via bone marrow transplant
44
What is characteristic of bones for osteopetrosis patients (on x-ray)
Sclerotic and bulbous ends
45
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?
Very low number of osteoclasts
46
What is osteoporosis?
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
What are the common sites of fracture for osteoporosis?
Wrist, hip, and spine
48
What are some major risk factors for osteoporosis?
Any of the following: age > 70, menopause < 45, hypogonadism, fragility fracture, malabsorption, immobilization, hip fracture in parents etc, etc, etc
49
What are the 3 major determinants of peak bone mass, when does that occur?
Genetics, physical activity, and nutrition peaking in the mid 20's
50
What role does menopause play in osteoporosis?
Decreased serum estrogen leads to increased IL-1, IL_6, and TNF levels, increased expression of RANK and RANKL = increased osteoclast activity
51
What role does age play in osteoporosis?
Decreased replicative activity of osteoprogenitor cells, decreased synthetic ability of osteoblasts, decreased biologic activity of matrix bound growh factors, and reduced physical activity
52
The mortality rate of osteoporosis is, in general, dependent on what?
The age when hip fracture occurs
53
What is paget disease of bone?
An imbalance between excessive osteoclast and osteoblast function; increased bone turnover
54
What are the 4 phases of paget disease of bone?
Osteolytic, mixed osteolytic-osteoblastic, osteoblastic and burnt-out stage
55
What are the key clinical points in paget disease?
Thick skull, deafness, kyphosis, pain, and bowed legs
56
What predominates in the sclerotic phase of paget disease?
irregular lamellar bone
57
What is osteomalacia due to?
Failure of bone to mineralize properly in an adult; dietary calcium deficiency or malabsorption
58
What is inadequate vitamin D or calcium in children called?
Rickets
59
For osteomalacia/rickets what stain is used and what does it show?
von Kossa stain shows calcified tissue as black
60
Renal osteodystrophy is due to?
Deficiency of 1,25(OH)2D due to tubular injury = hypocalcemia
61
What is the primary cause of hyperparathyroidism?
Adenoma
62
What is the secondary cause of hyperparathyroidism?
Prolonged hypoclacemia with compensatory hypersecretion (renal dz)
63
What is the result of either cause of hyperparathyroidism?
Unabated PTH secretion = release of mediateors that stimulate osteoclasts and bone resorption
64
What is a brown tumor?
Microfracture and hemorrhage; hemosiderin deposition; fibrosis; NOT a neoplasm; focus of increased osteoclast activity; expansile and spongy
65
What is osteitis fibrosa cystica?
Extension of brown tumor; pretty much a bunch of cysts brown tumors and hemorrhagic cysts

Rheum Lectures (7 decks)

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