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21 Cards in this Set

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what two troups are dz of muscle divided into?
1. neurogenic= distal wekaness, no pain, fasciculations present
2. myopathic= proximal weakness, +/- pain, no fasciculations
what characterizes neurogenic m. dz?
1. distal weakness
2. no pain
3. fasciculations present
what characterizes myopathic m. dz?
1. proximal weakness
2. +/- pain
3. no fasciculations
what is duchenne's muscular dystrophy?
1. x-linked lack of dystrophin
2. progressive proximal weakness and wasting beginning at age 1 yr
3. increased CPK
4. calf hypertrophy
5. Gower's maneuver
what are si/sx of duchenne's muscular dystrophy?
1. progressive proximal weakness and wasting
2. beginning at age 1 yr
3. increased creatine phosphate kinase
4. calf hypertrophy
5. waddling gait
6. Gower's maneuver (pts pick themselves off the floor by using arms to help legs)
what is Becker's dystrophy?
1. dystrophin levels are generally normal in Becker's, but protein qualitity of dystrophin is altered
2. may have nml lifespan, unlike Duchenne type (death occurs in 10-20s) most often d/t pneuomonia
what else characterizes duchenne muscular dystrophy?
1. intellectual retardation
2. skeletal deformities
3. m. contractures
4. cardiac involvment
5. increased CPK
what often occurs with polymyositis?
1. dermatomyositis
2. b/l proximal m. weakness
what are si/sx of polymyositis/dermatomyositis?
1. symmetric weakness/atrophy of proximal limb m.
2. cutaneous manifestation in dermatomyositis (Gottron's sign= scaly patches over the dorsum of proximal IP and MCP jts, periungual erythema, dilations of nailbed capillaries)
3. m. aches
4. dysphonia (laryngeal m. weakness)
5. dysphagia
what does dermatomyositis present with?
1. polymyositis
2. periorbital heliotropic red to purple rash
3. Gottron's sign= scaly patches over the dorsum of proximal IP and MCP jts
what is dx for polymyositis and dermatomyositis?
1. positive ANA
2. increased creatine kinase and aldolase (muscle nzs)
3. m. bx--shows inflamm changes
what is myasthenia gravis (MG)?
1. autoantibodies block the postsynaptic acetylcholine receptor
2. pts present with ptosis, diplopia, difficulty chewing/swallowing, respiratory difficulites, limb weakness
what may be a/c thymomas, throid and outher autoimmune dz (e.g. lupus, RA)?
1. myasthenia gravis (autoAbs blocking the postsynaptic acetylcholine receptor)
what are sx of myasthenia gravis?
1. m/c in women in 20-30s or men in 50-60s
2. m. weakness worse with use, diplopia, dysphagia,
3. proximal limb weakness which can progress to cause respiratory failure
what is the dx for myasthenia gravis?
1. trial of edrophonium (short-acting anticholinesterase) causes an immediate increase in strength
2. confirm c/ electromyelography--repetitive stimulation causes a decrease in action potential
what is pathopys of myasthenia gravis?
1. autoAbs binding to Ach receptors--cause m. weakness, ocular palsies, ptosis
2. when given a shrot acting anticholinesterase (edrophonium, neostigmine), m. weakness improves
what is lambert-eaton syndrome?
1. autoAb to PRE-synaptic Ca channels seen c/ small cell lung CA
2. causes defective release of Ach
how does MG differ from Lambert-Eaton?
Lambert-Eaton:
1. sx imporve c/ m. use
2. action potential strength increases with repeated stimulation

MG:
1. activity increases weakness of affected m.
2. repetitive stimulation decreases the action potential
what CA is Lambert-Eaton a/c?
1. small cell lung CA
2. defective release of Ach in response to a nerve impluse
what happens with aminoglycosides in MG?
1. aminoglycoside abx prevent the release of Ach from nerve endings
2. are particularly dangerous in pts with prexisting disturbances of neuromuscular transission (e.g. MG)
what is tx for MG?
1. anticholinesterase inhibitors (e.g. pyridostigmine) 1st line
2. steroids, cyclophosphamide, azathioprine for severe dz
3. plasmapheresis temporarily alleviates sx by removing the Ab
4. resection of thymoma can be curative