CH18 - Musculoskeletal Pathology Flashcards Preview

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Flashcards in CH18 - Musculoskeletal Pathology Deck (244)
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1

What is achondroplasia?

Impaired cartilage proliferation in the growth plate

2

What is achondroplasia a common cause of?

dwarfism

3

What is achondroplasia due to?

an activating mutation in fibroblast growth factor receptor 3 (FGFR3) Autosomal dominant

4

What does the overexpression of FGFA3 do?

It inhibits growth

5

What are most mutations for achondroplasia?

they are sporadic and related to increased paternal age.

6

What are the clinical features for achondroplasia?

Short extremities with normal-sized head and chest?

7

In achondroplasia, why is there short extremities with normal-sized head and chest?

its due to poor endochondral bone formation; intramembranous bone formation is not affected.

8

How is endochondral bone formation characterized?

by formation of a cartilage matrix, which is then replaced by bone; it is the mechanism by which long bones grow.

9

How is intramembranous bone formation characterized?

by formation of bone without a preexisting cartilage matrix; it is the mechanism by which fiat bones (e.g., skull and rib cage) develop.

10

In achondroplasia, what aspects are not affected?

Mental function, life span, and fertility are not affected

11

What is osteogenesis imperfecta?

It?s a congenital defect of bone resorption resulting in structurally weak bone

12

What is osteogenesis imperfecta most commonly due to?

an autosomal dominant defect in collagen type 1 synthesis

13

What is blue sclera?

thinning of scleral collagen reveals underlying choroidal veins.

14

What are the clinical features for osteogenesis imperfecta?

1) Multiple fractures of bone (can mimic child abuse, but bruising is absent) 2) blue sclera?3) Hearing loss

15

Why is there hearing loss in osteogenesis imperfecta?

Bones of the middle ear easily fracture

16

What is osteoporosis?

inherited defect of bone resorption resulting in abnormally thick, heavy bone that fractures easily

17

What is osteoporosis due to?

Its due to poor osteoclast function

18

What is an example for the multiple genetic variants that exist for osteoporosis?

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

19

In osteoporosis, why is there anemia in osteoporosis?

It is due to bony replacement of the marrow (myelophthisic process)

20

What are the clinical features for osteoporosis?

1) Bone fractures 2) Anemia, thrombocytopenia, and leukopenia with extramedullar hematopoiesis 3) Vision and hearing impairment 4) hydrocephalus 5) renal tubular acidosis

21

In osteoporosis, why is there vision and hearing impairment?

due to impingement on cranial nerves

22

In osteoporosis, why is there renal tubular acidosis?

Its seen with carbonic anhydrase II mutation, a lack of carbonic anhydrase results in decreased tubular reabsorption of HCO3 leading to metabolic acidosis.

23

What is the treatment for osteoporosis?

It is bone marrow transplant; osteoclasts are derived from monocytes.

24

What do Ricketts and osteomalacia result in?

Defective mineralization of osteoid

25

What do osteoblasts normally produce?

Osteoid which is then mineralized with calcium and phosphate to form bone

26

What are Rickets and osteomalacia due to?

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

27

What is vitamin D normally derived from?

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

28

What does activation of Vitamin D require?

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

29

What does active vitamin D do?

it raises serum calcium and phosphate

30

How does active Vitamin D raise serum calcium and phosphate?

by acting on the intestines, kidney and bone