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Neuromusculoskeletal & Psychiatry II Exam #3 > Pathology of Bones, Joints and Soft Tissue Part 1 > Flashcards

Pathology of Bones, Joints and Soft Tissue Part 1 Flashcards

1
Q

What are the major components of bone matrix? (3)

A

Osteoid - 35%

Mineral component - 65%

Type 1 collagen with small amounts of glycosaminoglycans and other proteins

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2
Q

What is the major protein in bone matrix?

What does it come from?

What is its function?

What is its use when measured in serum?

A

Osteopontin (AKA osteocalcin)

Osteoblasts

Ca++ homeostasis, mineralization, bone formation

It can help detect osteoblast activity

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3
Q

What provides the inorganic “hardness” of bone?

A

Hydroxyapatite (almost all of the body’s source of Ca++ and P)

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4
Q

What is the woven histologic form of bone?

What is the lamellar histologic form of bone?

A

Woven

  • produced rapidly: fetal development, fracture repair.
  • haphazard arrangement of collagen and less structural integrity.
  • abnormal in adults, but does not signal a bone disease necessarily.

Lamellar
-slow producing: parallel collagen; stronger.

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5
Q

Which cells regulate calcium and phosphorus levels?

A

Osteocytes - inactive osteoblasts with low cytoplasm

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6
Q

What is the function of osteoclasts?

A

They are macrophages derived from monocytes that function in bone resorption.

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7
Q

What is a resorption pit?

A

It is created by osteoclasts by utilizing surface integrins to attach and create a sealed trench to secrete MMPs which dissolve the bone.

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8
Q

What kind of ossification occurs in long bones vs. flat bone?

A

Long bone - endochondrial ossification using a cartilage mold. Deposits of new bone are made the growth plates and growth is longitudinal.

Flat bone - intramembranous ossification from deposition of bone on a pre-existing surface. Growth is appositional.

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9
Q

When is peak bone mass achieved?

What occurs after the 4th decade?

A

In early adulthood after cessation of skeletal growth.

Resorption > formation leading to decreased skeletal mass.

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10
Q

What is RANK, RANK-L and OPG?

A

RANK - receptor activator for NF-kB on osteclast precursors which triggers its differentiation to a mature osteoclast. It leads to breakdown of bone when activated by RANK-L.
RANK-L - ligand that is expressed on osteoblasts and bone marrow stromal cells.

OPG - “decoy” receptor made by osteoblasts to inhibit RANK and RANK-L interaction. Builds bone and prevents differentiation.

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11
Q

What is the role of WNT/B-catenin in bone remodeling?

What inhibits this pathway?

A

Binds LRP receptors on osteoblasts and activates production of OPG -> builds bone.

Sclerostin (produced by osteocytes) inhibits this pathway.

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12
Q

The balance of net bone formation vs. net bone resorption is modulated by…

A

RANK (breakdown) and WNT (build)

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13
Q

What hormones trigger building of bone?

Which hormones trigger breakdown of bone?

A

Build: estrogen, testosterone, vitamin D

Breakdown: PTH, IL-1, glucocorticoids

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14
Q

What is the role of M-CSF?

A

It is a receptor on osteoclast precursors that stimulate the tyrosine kinase cascade that is needed for generation of osteoclasts.

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15
Q

At what age are developmental disorders of bone detected?

A

Adulthood

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16
Q

What is Dystosis?

A

Migration and condensation of mesenchyme and differentiation into cartilage anlage.

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17
Q

What transcription factor defect can cause problems with Dystosis?

A

Homeobox genes - leads to abnormal differentiation in osteoblasts and chondrocytes.

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18
Q

What gene is implicated in the development of Bradydactyly types D and E?

A

HOXD13 - short terminal phalanges of thumb and big toe.

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19
Q

Cleidocranial dysplasia is associated with which gene?

What is the inheritance?

What are features of it?

A

RUNX2

AD

Wormian bones (extra bones within cranial sutures), delayed eruption of secondary teeth, primitive clavicles, short height, patent fontanelles, delayed closure of sutures.

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20
Q

Achondroplasia has what inheritance and what gene is involved?

What is the overall effect of the disease?

A

AD; FGFR3 gain of function.

Retarded cartilage growth with short extremities, but normal trunk length and large head.
There is no change in longevity or intelligence or reproductive ability.

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21
Q

Thalantophoric dysplasia has what mutation?

What is the major/serious structural abnormality?

What is the prognosis?

A

FGFR3 gain of function.

Small chest cavity -> respiratory insufficiency.

Death at birth or soon after.

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22
Q

LPR5 receptor mutation leads to =

RANKL mutation lead to =

A

LPR5 receptor = either osteoporosis or osteopetrosis depending on defect.

RANKL = decreased or absent osteoclasts.

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23
Q

What is the most common inherited disorder of CT?

A

Type I collagen disorders - osteogenesis impecta.

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24
Q

Osteogenesis imperfecta has effects on which structures?

What part of the type I collagen is affected?

A

Bone, but also joints, eyes, ears, skin and teeth (blue sclera, hearing loss and dental problems).

a1 and a2 chains of type I collagen.

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25
Q

What are features of type I OI?

A

Normal lifespan with fractures in childhood that decrease in frequency following puberty.

  • collagen structure is normal, but there us less than a normal amount.
  • may have brittle teeth, hearing loss and blue/purple/gray sclerae.
  • minimal bone deformity, if any.
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26
Q

How many sub-types of OI exist? Which is best to have?

A

4 - type 1 is best, type 2 is worst. (1, 4, 3. 2)

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27
Q

What are classic features of type III OI?

A

Fractures present at birth; XRs may reveal multiple fractures that have healed by time of birth.

  • triangular face
  • short stature
  • blue/gray/purple sclerae
  • loose joints and poor muscle developent
  • barrel-shaped rib cage
  • severe bone deformity
28
Q

What are classic features of type II OI?

A

No triple helix, uniformly fatal in utero due to respiratory problems and underdeveloped lungs, massive bone fragility and many intrauterine fractures.

29
Q

What are classic features of type IV OI?

A

Bone fractures mostly before puberty.

  • sclera are white
  • spinal curvature
  • barrel-shaped rib cage
  • triangular face
30
Q

Osteopetrosis (Marble Bone or Albers-Schonberg disease) is due to a mutation in what gene?

What other abnormality may be seen?

What is the major bone abnormality?

A

Mutation in CLCN7 which leads to carbonic anhydrase 2 deficiency and dysfunction of osteoclasts.

Renal tubular acidosis.

Bones lack a medullary cavity (Erlenmyer flask), have bulbous ends and compress small nerves (small foramina).

31
Q

What is seen in severe vs. mild forms of Osteopetrosis?

What are the inheritance of each?

A

Severe: AR; CN defects - optic atrophy, deafness and facial paralysis.
-postpartum mortality: fractures, anemia and hydrocephaly.

Mild: AD; repeated fractures in adolescence or adulthood.
-mild CN defects and anemia.

32
Q

What are Mucopolysaccharidoses?

What enzymes are mostly affected?

What is seen on histology?

A

Lysosomal storage disease caused by mutations in enzymes that degrade dermatan sulfate, heparan sulfate and keratan sulfate.

Acid hydrolase enzymes.

Mucopolysaccharide accumulation in chondrocytes, causing apoptosis, and within the extracellular space.

33
Q

Osteopenia =

Osteoporosis =

A

Decreased bone mass (1-2.5 SD below the mean).

Osteopenia severe enough to increase risk of fracture (>2.5 SD below the mean).

34
Q

Osteoporosis is signified by…

What are the most common forms? (2)

A

Atraumatic or vertebral compression fracture.

Senile and postmenopausal.

35
Q

What is senile osteoporosis?

A

Age-related osteoporosis due to low proliferative and biosynthetic potential (poor ability to make bone).
Decreased cellular response to GFs.

36
Q

What is the relationship between Ca++ and girls in adolescence?

A

They don’t have enough Ca++ intake during the period of rapid growth which restricts their bone mass.

37
Q

What is the role of estrogen in osteoporosis?

What “variant” of osteoporosis is this?

A

Decreased estrogen (post-menopause) increases both resorption and formation, but resorption much more so. Estrogen activates RANKL and decreases OPG.

High turnover variant.

38
Q

Which cytoines play a role in postmenopausal osteoporosis?

A

IL-6, TNF-a, IL-1

39
Q

Postmenopausal osteoporosis causes what morphologic changes to bone? (3)

A

Increased osteoclast activity.

Bones increase their surface area.

Trabeculae is perforated, thinned and have loose interconnections which cause microfractures and vertebral collapse.

40
Q

What morphologic change is seen in senile osteoporosis?

A

Cortex is thinned by subperiosteal and endosteal resorption.

41
Q

Risk factors for osteoporosis:

Genetic
Nutrition
Environmental

A

Genetic - Caucasian, light colored hair and eyes.

Nutrition - Ca++ deficiency in teen years, P overload.

Environmental - smoke.

42
Q

What causes the loss of height in osteoporosis?

What are 2 major complications f fractures in these patients?

A

Lumbar lordosis and kyphoscoliosis.

PE and pneumonia.

43
Q

Paget Disease (AKA Osteitis Deformans) is characterized by what changes to bone?

What bones/regions are most commonly fractures?

What age is most common?

What countries are most common?

What is the pathogenesis?

A

Increased, but disordered and structurally unsound bone mass.

Axial skeleton in 80% of cases.

Average age of diagnosis is 70.

Caucasian majority countries: England, France, USA, other European countries, Australia, etc.

Both environmental and genetic:

  • 40-50% is familial.
  • 5-10% of sporadic mutations in SQSTM1 gene which activates NK-kB and osteoclast activity.
44
Q

What feature is seen on XR of the skull in a patient with Paget Disease?

A

“Cotton wool”

45
Q

What is the morphologic hallmark of Paget disease?

What are the 3 phases?

Is there a risk of cancer due to PD?

A

Mosaic pattern of lamellar bone, seen in the sclerotic phase.
Jigsaw-like appearance with prominent cement lines - haphazardly oriented units of lamellar bone.

  1. Initial phase: large osteoclasts with 100 nuclei.
  2. Mixed phase: clasts persist, but lost of blasts also.
  3. Final: burned-out quiescent osteoclastic stage.

1% risk of sarcomatous transformation, often osteosarcoma or fibrosarcoma.

46
Q

What bones are fractured in Paget disease?
How ware the fractures characterized?

What is seen cutaneously? What is the complication of this?

What are common lab findings?

What is the treatment?

A

Weight-bearing: bowing of femurs, tibia, distortion of fibular head. This leads to secondary OA.
“Chalk-stick” fractures in long bones of the legs.
Compression fractures of spine produce spinal cord injury and kyphosis.

Hpervascularity of Paget bone warms the overlying skin and the increased blood flow acts as an AV shunt and can cause HOHF.

Increased serum ALP with normal Ca++ and P.

Calcitonin and biphosphonates to suppress symptoms.

47
Q

“Rachitic rosary” of ribs =

A

Rickets

48
Q

“Railroad track” appearance of trabeculae =

A

Dissecting osteitis - clasts tunnel and dissect centrally along the length of the trabeculae creating the raiload track appearance.

49
Q

von Recklinghausen disease of bone

A

Increased bone cell activity, peritrabecular fibrosis and cystic brwn tumors is a hallmark of severe hyperparathyroidism = generalized osteitis fibrosis cystica.

50
Q

What 3 mechanisms lead to skeletal abnormalities due to kidney disease?

A

Tubular dysfunction: RTA with low pH dissolves hydroxyapatite leading to demineralization of the matrix and osteomalacia.

Generalized RF: glomerular and tubular dysfunction leading to chronic hyperphosphatemia and hypocalcemia and ultimately secondary hyperparathyroidism.

Decreased production of secreted factors leading to low vitamin D.

51
Q

“Silent crippler” =

A

Renal osteodystrophy in kids due to its slow and chronic nature.

52
Q

Types of fractures:

Single
Compound
Communicated
Displaced
Stress
"Greenstick"
Pathologic
A

Single - skin intact.

Compound - bone breaks the skin.

Communicated - bone is fragmented.

Displaced - end of bones are not aligned.

Stress - slowly developing fractures following a period of activity.

“Greenstick” - extending only partially through the bone, commonly in infants when bones are soft.

Pathologic - fracture due to underlying disease process.

53
Q

What is seen after 1 week of the bone healing process?

After 2 weeks?

What is the last part to heal?

A

Soft tissue callus or procallus: fusiform and predominately uncalcified.

Callus is transformed into a bony callus (max girth after 2nd to 3rd week).

Restoration of medullary cavity.

54
Q

What is Osteonecrosis?

What are cases most commonly from?

A

Infarction of bone and marrow (fairly common).

Fractures or corticosteroid therapy (iatrogenic).

55
Q

Symptoms of Osteonecrosis depend on location and extent of infarct. What are the symptoms of the following?

Subchondral infarcts

Medullary infarcts

A

Subchondral infarcts: pain and initially associated only with activity, then becomes constant. May collapse and lead to severe secondary OA.

Medullary infarcts: small and clinically silent, except in Gaucher disease, dysbarism (“bends”) and sickle cell anemia.

56
Q

What is the morphology of medullary infarcts?

What area is not usually affected? Why?

A

They are geographic and involve trabecular bone and marrow.

Cortex due to collateral flow.

57
Q

What is the morphology of subchondral infarcts?

A

Triangular or wedge-shaped with the subchondral bone plate as its base.

Dead bone: empty lacunae surrounded by necrotic adipocytes that commonly rupture.

Trabeculae that remain intact act as a scaffolding for new bone - “creeping substitution”

58
Q

What is the most common cause of Osteomyelitis?

A

Pyogenic bacteria and mycobacteria. However, viruses and fungi can cause it, too.

59
Q

How does pyogenic osteomyelitis spread in healthy kids?

How does it occur in adults?

What bug constitutes 80-90% of culture positive osteomyelitis?

A

Hematogenous spread from trivial mucosa injuries (defecation or chewing hard foods) or minor skin infections.

Usually a complication of open fractures, surgery and diabetic infections of the feet.

S. aureus.

60
Q

In which patients/conditions would you expect the following causes of osteomyelitis?

E. coli, Pseudomonas and Klebsiella

Mixed bacteria

Haemophilus influenzae and Grp. B Strep

Salmonella

Neisseria deficiency

A

E. coli, Pseudomonas and Klebsiella - UTIs or IVDU.

Mixed bacteria - during surgery or open fractures.

Haemophilus influenzae and Grp. B Strep - “frequent pathogens” (?).

Salmonella - sickle cell patients.

Neisseria deficiency - C5,6,7,8, and 9 (MAC) deficiency.

61
Q

Acute osteomyelitis in kids causes what?

What is sequestrium?

A

Periosteal abscesses and dissect along the bone surface.

Rupture of the periosteum -> soft tissue abscess which can become a “draining sinus”. The sequestrium may crumble and release its fragments into the sius.

62
Q

What does osteomyelitis cause in infants?

A

Septic or suppurative arthritis and can cause permanent disability (rare in adults).

63
Q

What is involucrum in chronic osteomyelitis?

What are Brodie abscesses?

What is sclerosing osteomyelitis of Garre?

A

The shell of living tissue that surrounds the segment of devitalized bone.

Small interosseous abscess that involves the cortex and is walled off by reactve bone.

Jaw has extensive new bone formation that obscures the underlying osseous structure.

64
Q

Mycobacterium osteomyelitis occurs usually via..

What is its progression?

What are symptoms?

What is seen on histology?

A

Blood borne from visceral disease; occasionally by direct extension.

It may persist for years before detected, but is more resistant and destructive than pyogenic osteomyelitis.

Localized pain, low-grade fevers, chills and weight loss.

Caseating necrosis and granulomas.

65
Q

What is Tuberculous Spondylitis (Pott Disease)?

What is permanent in this disease?

What are complications?

A

Bone infection of the spine in approximately 40% myobacteial osteomyelitis cases.

Permanent compression fractures leading to kyphosis, scoliosis and neurological defects due to compression.

Tuberculous arthritis, sinus infections,psoas abscesses and amyloidosis.

66
Q

What can congenital syphilis cause?

A

Bone lesions appear about 5 months gestation and fully developed at birth.
-Saber shin: massive reactive periosteal bone deposition on medial and anterior surfaces of the tibia.

67
Q

What can acquired syphilis cause?

A

Bone disease beginning in tertiary stage, 2-5 years after initial infection.
-Saddle nose: palate, skull and extremities (tibia especially) are involved.

Neuromusculoskeletal & Psychiatry II Exam #3 (12 decks)

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