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MSK/Derm > SM 233: Metabolic Disease > Flashcards

SM 233: Metabolic Disease Flashcards

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Dermatology Board Prep flashcards
1
Q

What is the Axial skeleton?

A

Vertebra and ribs derived from para-axial plate mesoderm

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2
Q

What is the embryonic origin of the Axial skeleton?

A

Para-axial plate mesoderm

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3
Q

What is the Appendicular skeleton?

A

Arms and Legs and hip derived from lateral plate mesoderm

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4
Q

What is the embryogenic origin of the Appendicular skeleton?

A

Lateral plate mesoderm

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5
Q

What are the cranofacial bones of the skeleton derived from?

A

Neural crest

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6
Q

Describe the composition of the normal skeletal system?

A

70% inorganic matrix (Calcium Hydroxyapatite) 30% organic (Type I collagen and Osteocalcin)

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7
Q

What is Osteocalcin?

A

A serum marker of bone formation and density

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8
Q

Which region of bone contains hematopoeitic cells?

A

The Medullary cavity, with medullary bone

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9
Q

Which region of bone is normally made of compact bone?

A

The cortex

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10
Q

What is intramembranous bone formation?

A

Minor contributor, bone develops from Collagen undifferentiated osteoprogenitor cells and produces flat bones of skull and clavicles

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11
Q

What is endochondral bone formation?

A

Major contributor, bone develops from epiphyseal cartilage of the growth plate, forming the appendicular and axial skeleton

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12
Q

What are the 5 zones of Endochondral Bone formation?

A

Resting Zone

Zone of Proliferation

Zone of Hypertrophy

Zone of Calcification

Primary Trabeculae

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13
Q

What factors stimulate endochondral bone formation and cartilage growth, and where do they act?

A

PTHrP and BMP at the Zone of Proliferation

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14
Q

What factors inhibit endochondral bone formation and cartilage growth, and where do they act?

A

FGF, at the Zone of Proliferation

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15
Q

Which diseases can be traced back to the Zone of Proliferation?

A

Achondroplasia

Mucopolysaccharidosis

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16
Q

Which diseases can be traced back to the Zone of Provisional Calcification?

A

Rickets/Osteomalacia

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17
Q

Which diseases can be traced back to the Primary Trabeculae in endochondrail bone formation?

A

Osteogenesis Imperfecta
Scurvy
Osteoperosis

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18
Q

What are the two types of bone?

A

Immature (Osteoid and Woven)
Mature (Lamellar)

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19
Q

What is Osteoid?

A

Unmineralized poorly organized bone matrix composed of Type I collaged formed rapidly

Mineralization needed to become adult bone

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20
Q

What is Woven bone?

A

Mineralized immature bone formed rapidly, and the main componenet of prepubertal bone

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21
Q

What is lamellar bone?

A

Mature bone with parallel Type I collagen fibers that form Lamellae and evenly distributed osteocytes

Two types: Cortical and Cancellous

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22
Q

What is cortical bone?

A

Cortical = compact bone that is initially part of a lamellae which laters becomes part of a Haverisian canal when Collagen deposits to handle stress

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23
Q

What is cancellous bone?

A

Cancellous = spongy bone formed by endochondral ossification, found in the center of long bones

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24
Q

What are Osteoblasts?

A

Bone forming cellls that produce Matrix proteins, Type I collagen, and initiate mineralization

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25
Q

What cell surface receptors are found on Osteoblasts?

A

PTH, Vit D, Estrogen

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26
Q

What are Osteocytes and what key molecule do they produce?

A

Ostoecytes are osteoblasts that are incorporated into mature bone

Osteocytes produces Sclerostin, a protein that inhibits further bone formation until osteocytes are stimulated

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27
Q

What is Sclerostin?

A

A protein made by Osteocytes that inhibits further bone formation until the Osteocytes are stimulated

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28
Q

What are Osteoclasts?

A

Multinucleated cells formed from monocytes in response to RANK-Ligand secred by osteoblasts

Mediate bone resorption

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29
Q

What are resorption pits?

A

Pits on the surface of bone where Osteoclasts are found

30
Q

How do Osteoblasts give rise to Osteoclasts?

A

Ostoblasts express RANK-Ligand

Osteoclast precursors express RANK Receptor

Osteoblast RANK-Ligand binds Osteoclast precursor RANK Receptor to differentiate precursor into Osteoclast

31
Q

What is the function of an Osteoclast “resorption pit”?

A

Creates a sealed environment where Osteoclast H/K ATPases can acidify to high concentration and break down bone

32
Q

How do Osteoclasts break down bone?

A

Osteoclast use a H ATPase to break down bone and release minerals and growth factors from bone

Osteoperosis can arise from mutations in H ATPase

33
Q

How do Osteoblasts and Osteoclasts form a cycle that promotes bone remodeling continually?

A

Osteoblasts build bone and activate Osteoclasts via RANK-Ligand to Rank-Receptor signalling respectively

Osteoclasts chew up bone and release growth factors from bone

Growth factors from bone further stimulate Osteoblasts

34
Q

Why is it important that bone remodeling is continuous?

A

Dissipates bone stress over life and allows for bone to act as a repository of minerals

35
Q

How are Osteons formed in Cortical bone?

A

Osteons form in response to stress

Osteoclasts first resorb bone = primary osteon

Osteoblasts fill cavity made by Oclasts in concentric Lamellae

Osteocytes in the newly formed Osteon regulate remodelling

36
Q

How is Trabecular bone formation controlled?

A

Osteoclasts are activated
Resporb bone in their pits = Howship’s Lacuna

Reversal of cell type to Osteoblasts

Bone formatino occurs

37
Q

What can cause Acute Osteomyelitis, broadly speaking?

A

Hematogenous spread (bacterimia)

Contiguous spread from abscess or ulcer

Direct inoculation into bone

Ischema from vascular insufficiency

38
Q

What is the most common cause of Acute Osteomyelitis and why is it hard to treat?

A

S. aureus

New bone forms around dead/infected bone, so it’s hard for antibiotics to reach

Treat with surgical debridement/removal of bone and long course of antibiotics

39
Q

What is Osteogensis Imperfecta and what causes it?

A

A group of diseases with AR inheritance most severe and lethal in the perinatal period

Defect in synthesis of Type I collagen

40
Q

What’s worse, abnormal Type I collagen or insufficient Type I collagen?

A

Abnormal Type I collagen, because it disrupts the strcutre of bone in Osteogensis Imperfecta

41
Q

How does Osteogensis Imperfecta present?

A

Presentation reflects deficient Type I Collagen:

Bone fractures + excess callus formation

Blue Sclera

Hearing Defects

Teeth Defects

42
Q

Which zone of Endochondral ossification is affected by Osteogenesis Imperfecta?

A

The Zone of Primary Trabeculation, since the Type I collagen is defective and mature bone can’t form normally, resulting in lots of weak, woven bone

43
Q

What defines Osteoperosis?

A

1+ atraumatic bone fractures (bone insufficiency)

OR

Low bone mineral density on DXA scan

44
Q

What are the two broad categories of Osteoperosis?

A

Localized due to immobility/regional inflammation

Generalized due to Age/PMP status

45
Q

What causes localized Osteoperosis?

A

Immobility leading to Atrophy

Inflammation around a specific bone like RA

46
Q

What general principles underlie Senile and PMP Osteoperosis?

A

Osteoblasts lose ability to form new bones

Growth factors lose potency

Osteoclasts become activated

47
Q

What causes PMP Osteoperosis and what bones are effected most?

A

Estrogen deficiency results in a disinhibition of Osteoclasts, leading to rapid bone breakdown

Affects bones with large surface area (vertebrae)

48
Q

What is a high turnover osteoperosis, and give an example?

A

Osteoperosis driven primary by increased Osteoclast activity as opposed to deceased Osteoblast activity

Ex = PMP Osteoperosis

49
Q

What is Senile Osteoperosis and who gets it?

A

Men and Women older than 70

Due primarily to Osteoblasts having less activity with age and growth factors becoming less potent

50
Q

What type of fractures are common in Senile Osteoperosis?

A

Hip and Vertebra

51
Q

What is a low turnover osteoperosis, and what is an example?

A

An osteoperosis driven by loss of activity of osteoblasts with normal osteoclast activity

Ex = Senile Osteoperosis

52
Q

What are Mucopolysaccharidoses?

A

Diseases caused by mutations in lysosomal enzymes that degraded GAGs resulting their accumulation and cellular damage

53
Q

What are the signs and symptoms of Mucopolysaccharidoses?

A

Presentation varies by the enzyme effected, causing a different resulting Mucopolysaccharidoses:

Cardiac valvular disease

Mental retardation

Macroglossia

54
Q

How can Mucopolysaccharidoses be diagnosed?

A

Diagnosed prenatally by measuring enzyme activity in cultured placenta-derived cells or by measuring urinary GAG

55
Q

What is the mode of inheritance of most Mucopolysaccharidoses?

A

Mostly Autosomal Recessive
Hunter Syndrome is X-linked Recessive

56
Q

What diseases are associated with a Vit D deficiency?

A

Rickets and Osteomalacia

57
Q

What are the effects of Vit D?

A

Increased Ca and PO4 reabsorption from the intestine

58
Q

How does Vit D relate to endochondral bone formation?

A

In kids, Vit D is required for calcifiation of Cartilage in the growth plate at the Zone of Provisional Calcification; deficiency = Rickets

In adults, Vit D is required for conversion of osteoid to new adult bone; deficiency = Osteomalacia

59
Q

How does a Vit D defiency effect kids?

A

Vit D deficiency causes growth plate to widen with uncalcified cartilage and osteoid because Vit D is needed for calcification

= Rickets

60
Q

How does Rickets effect bones?

A

Rickets can cause bowing of the femoral bones and large costochondral spots on the rib cage

Also makes all bones weaker

61
Q

How does a Vit D defiiency effect adults?

A

Vit D deficiency results in the inability to calcify osteoid to form new adult bone during remodeling

Usually due to chronic renal failure

62
Q

How does Hyperparathyroidism manifest?

A

Moans (GI Tract)
Bones (Aches)

Renal Stones

Psychiatric Overtones

63
Q

What is the difference between primary hyperparathyroidism and secondary hyperparathyroidism?

A

Primary HPT is due to overactivity of the Parathyroid itself, due often to Parathyroid adenoma

Secondary HPT is often driven by renal failure and decreased serum Ca triggering excess PTH release

64
Q

How does elevated PTH effect bone cells?

A

PTH activates osteoclasts and causes osteoperosis

65
Q

What is the brown tumor of the bone?

A

In Hyperparathyroidism, osteoclasts are activated and form “cutting cones” that break down bone

Severe HPT results in fractures that cause intramedulllary hemorrhage and fibrosis within these “cutting cone” derived cracks in the bone

66
Q

What is Paget’s Disease of Bone?

A

“Collage of Matrix Madness” due to dyssyncrhony of osteoclastic/osteoblastic activity

Effects multiple bones causing fractures, spinal nerve compression, and high output cardiac failure

67
Q

Explain the pathophysiology of Paget’s Disease of Bone?

A

Due to dyssynchrony betwen Osteoclasts and Osteoblasts, obseve sharp cycles of bone resportion followed by bone formation

Upregulation of NFKB-Osteoclastogensis

3 phases: osteolytic, “mixed” osteolytic osteoblastic, and sclerotic

68
Q

What disease is characterized by a mosaic of cement lines in thickened bones?

A

Paget’s disease

69
Q

What is Osteopetrosis?

A

A disease of absent or deficient osteoclast activity, due to defficient H+ ATPase activity resulting in abnormally thickened bone

70
Q

What clinical features are associated with Osteopetrosis?

A

Thickened bone

Fractures due to loss of Osteon formation

Anemia due to loss of Medullary bone spaces from bone thickeing

Cranial nerve defects and Radiculopathy due to thickening of bone leading to compression of nerves

71
Q

Which zone of endochondral bone formation does Osteopetrosis effect?

A

Osteopetrosis effects the Zone of Primary Bone Trabeculae formation because this is where osteoclasts activity would occur

MSK/Derm (46 decks)

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