Skeletal mm Pathology (7) Flashcards
what is sarcoplasmic hypertrophy
Primary due to increased glycogen storage
What do satellite cells do
Facilitate growth, maintaenance and repair of damaged skeletal mm tissue
What is the role of fibroblast growth factor
proliferation and differentiation of satelite cells, leading to skeletal mm hypertrophy (amount released is proportional to degree of mm trauma)
what is rhabdomyolysis and what does it release into circulation
Widespread acute necrosis of skeletal mm fibres
–releases into circulation systolic proteins such as myoglobin (crash-syndrome)
What is trichinosis due to and what does it cause
Trichinella spiralis inf
-mm pain, periorbital edema, splinter hemorrhages
Clostridium tetani- transmission, s/s
trans- spores in soil enter body, 2 day incubation
ss- begins w mm stiffness in jaw, lockjaw, slightest stim causes generalized, painful mm contractions
What is duchennes muscular dystrophy characterized by
Characterized by progressive degen of mm particularily those in pelvis/shoulder girdles
Genetics of ducheenes mm dystrophy and rate
X linked recessive
1:3500 male births
Pathogenesis of ducheene dystrophy
- relentless necrosis of mm
- # of mm cells decreases progressively
- replaced by fibroadipose tissue (pseudohypertrophy)
Dx of ducheene mm dystrophy and when is it evident clinically
Dx: PCR detection of abnormal DNA from leukocytes, increased serum kinase
clinical- not detectable during first year (evident by 3/4 years)
What causes death in ducheene mm dystrophy
complications of respiratory insufficiency caused by mm weakness
-cardiac arrhythmia owing to myocardial involvement
Differences bw ducchenes and becker
becker- typically milder/later onset, truncated protein
ducheene: absence of dystrophin
Myotonic dystrophy- rate, genetics
Mc adult mm dystrophy
autosomal dominant
-trinucleotide repeat disorder on chromosome 19 (on myotonic dystrophy pro kinase gene)
s.s of myotonic dystrophy
-testicular atriphy, glu intolerence, mm wasting, cardiac defects
what is myasthenia gravis and what does it affect
antibodies to the Ach receptor at the myoneural junction (destroy via complement system)
What does myasthenia gravis cause
-impaired signal trans (mm weakness, fatigue)
What is lambert-eaton syndome
-Paraneoplastic disorder where igG autoanibodies traget voltage sensitive calc channels expressed in motor nerve terminal and in cells of lunch cancer
What does paraneoplastic disorder cause
manifests as mm weakness, wasting and fatigability of prox limbs/ trunk
Pathological changes in rhabdomyolysis
an active, non inflammatory myopathy w scattered necrosis of mm fibres
-causes mm to be swollen, tender and profoundly weak
s/s of rhabodomyolosis
- pain (first sym)
- dark urine
- renal insuffiencieny
- creatine kinase elevation
What is crush syndrome
traumatic rhabdomyoloysis due to natural disaters etc
what is denervation
lesions of LMN
-progressive invariably atrophy of a skeletal mm fibre due to interrupted connection w LMN
What is spinal muscular atrophy and what is it due to
- 2nd mc letal autosonmal recessive disorder after cystic fibrosis
- Surviva mm neuron gene (SMN1) is absent in virtually all cases
what is steroid myopathy due to and causes
- Due to corticosteroid therapy (large doses)
- serum kinase not always elevated
- severe mm weakness
What does statin induced myopathies cause, blood markers
-prox mm weakness occurring during or after tx w statins
- elevated creatine kinase
- persistece of weakness and elevated CK despite discontinuation
What are the 2 noninfectious inflammatory myopathies and what characterizes them
-group of immune mediated disorders w symetrical mm invlvment
- Polymyositis
- Dermatomyositis
Polymyositis- age, gender, risks
Female dominant
- black pop
- 40-60
risk- increased risk of malignant neoplasms
pathogeneis of polymyositis
-cytotoxic CD8 t cells and CD4 cells activate macrophages to damage unidentified antigens in myocyte fibres in skeletal mm
triggers of polymyositis
triggers for t cell response may be associated with HIV, Coxsackie virus B
Clincial findings of polymyositis
- constitutional signs
- symetrical prox weakness
- dysphagia
- respiratory difficulties
mm atrophy not feature
lab findings of polymyositis
- Serum CK and aldolase increased
- Serum ANA increased
Dermatomyositis- etiology +pathogenesis
activated cd4 t cells primarily target the capillaries in skeletal mm
-antibodies and complement are involved in the capillary damage
Clinical findings of dermatomyositis
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
