Skeletal mm Pathology (7)

Question 1

what is sarcoplasmic hypertrophy

Answer 1

Primary due to increased glycogen storage

Question 2

What do satellite cells do

Answer 2

Facilitate growth, maintaenance and repair of damaged skeletal mm tissue

Question 3

What is the role of fibroblast growth factor

Answer 3

proliferation and differentiation of satelite cells, leading to skeletal mm hypertrophy (amount released is proportional to degree of mm trauma)

Question 4

what is rhabdomyolysis and what does it release into circulation

Answer 4

Widespread acute necrosis of skeletal mm fibres

–releases into circulation systolic proteins such as myoglobin (crash-syndrome)

Question 5

What is trichinosis due to and what does it cause

Answer 5

Trichinella spiralis inf

-mm pain, periorbital edema, splinter hemorrhages

Question 6

Clostridium tetani- transmission, s/s

Answer 6

trans- spores in soil enter body, 2 day incubation

ss- begins w mm stiffness in jaw, lockjaw, slightest stim causes generalized, painful mm contractions

Question 7

What is duchennes muscular dystrophy characterized by

Answer 7

Characterized by progressive degen of mm particularily those in pelvis/shoulder girdles

Question 8

Genetics of ducheenes mm dystrophy and rate

Answer 8

X linked recessive

1:3500 male births

Question 9

Pathogenesis of ducheene dystrophy

Answer 9

• relentless necrosis of mm
• # of mm cells decreases progressively
• replaced by fibroadipose tissue (pseudohypertrophy)

Question 10

Dx of ducheene mm dystrophy and when is it evident clinically

Answer 10

Dx: PCR detection of abnormal DNA from leukocytes, increased serum kinase

clinical- not detectable during first year (evident by 3/4 years)

Question 11

What causes death in ducheene mm dystrophy

Answer 11

complications of respiratory insufficiency caused by mm weakness
-cardiac arrhythmia owing to myocardial involvement

Question 12

Differences bw ducchenes and becker

Answer 12

becker- typically milder/later onset, truncated protein

ducheene: absence of dystrophin

Question 13

Myotonic dystrophy- rate, genetics

Answer 13

Mc adult mm dystrophy

autosomal dominant
-trinucleotide repeat disorder on chromosome 19 (on myotonic dystrophy pro kinase gene)

Question 14

s.s of myotonic dystrophy

Answer 14

-testicular atriphy, glu intolerence, mm wasting, cardiac defects

Question 15

what is myasthenia gravis and what does it affect

Answer 15

antibodies to the Ach receptor at the myoneural junction (destroy via complement system)

Question 16

What does myasthenia gravis cause

Answer 16

-impaired signal trans (mm weakness, fatigue)

Question 17

What is lambert-eaton syndome

Answer 17

-Paraneoplastic disorder where igG autoanibodies traget voltage sensitive calc channels expressed in motor nerve terminal and in cells of lunch cancer

Question 18

What does paraneoplastic disorder cause

Answer 18

manifests as mm weakness, wasting and fatigability of prox limbs/ trunk

Question 19

Pathological changes in rhabdomyolysis

Answer 19

an active, non inflammatory myopathy w scattered necrosis of mm fibres

-causes mm to be swollen, tender and profoundly weak

Question 20

s/s of rhabodomyolosis

Answer 20

• pain (first sym)
• dark urine
• renal insuffiencieny
• creatine kinase elevation

Question 21

What is crush syndrome

Answer 21

traumatic rhabdomyoloysis due to natural disaters etc

Question 22

what is denervation

Answer 22

lesions of LMN

-progressive invariably atrophy of a skeletal mm fibre due to interrupted connection w LMN

Question 23

What is spinal muscular atrophy and what is it due to

Answer 23

• 2nd mc letal autosonmal recessive disorder after cystic fibrosis
• Surviva mm neuron gene (SMN1) is absent in virtually all cases

Question 24

what is steroid myopathy due to and causes

Answer 24

• Due to corticosteroid therapy (large doses)
• serum kinase not always elevated
• severe mm weakness

Question 25

What does statin induced myopathies cause, blood markers

Answer 25

-prox mm weakness occurring during or after tx w statins

• elevated creatine kinase
• persistece of weakness and elevated CK despite discontinuation

Question 26

What are the 2 noninfectious inflammatory myopathies and what characterizes them

Answer 26

-group of immune mediated disorders w symetrical mm invlvment

1. Polymyositis
2. Dermatomyositis

Question 27

Polymyositis- age, gender, risks

Answer 27

Female dominant

• black pop
• 40-60

risk- increased risk of malignant neoplasms

Question 28

pathogeneis of polymyositis

Answer 28

-cytotoxic CD8 t cells and CD4 cells activate macrophages to damage unidentified antigens in myocyte fibres in skeletal mm

Question 29

triggers of polymyositis

Answer 29

triggers for t cell response may be associated with HIV, Coxsackie virus B

Question 30

Clincial findings of polymyositis

Answer 30

• constitutional signs
• symetrical prox weakness
• dysphagia
• respiratory difficulties

mm atrophy not feature

Question 31

lab findings of polymyositis

Answer 31

• Serum CK and aldolase increased

- Serum ANA increased

Question 32

Dermatomyositis- etiology +pathogenesis

Answer 32

activated cd4 t cells primarily target the capillaries in skeletal mm

-antibodies and complement are involved in the capillary damage

Question 33

Clinical findings of dermatomyositis

Answer 33

mm complaints are similar to those in polymyositis
Atrophy is prominent fx

• reddish-purple papules called gottron patches are noted over knuckles and PIPs
• purple/red eyelid discoloration occurs