Diseases of Muscle Flashcards
myopathy definition
pathological disorder that impairs normal muscle function (physiology), usually but not always with alteration of muscle structure (anatomy)
- nonfatiguable
- symmetric
- PROXIMAL muscle weakness (except for inclusion body myositis)
- NO sensory symptoms
- NO atrophy
- tendon reflex loss equal to strength loss
impaired function, asthenia, fatigue in isolation suggests ________
suggests NOT neuromuscular disease
-likely a myopathy
types of weaknesses common with myopathy
- HIP GIRDLE (getting up from chair, stairs)
- Shoulder girdle (reaching, lifting)
- OCCULOMOTOR (ptosis, diplopia)
- FACIAL (trouble with balloons, straws)
- BULBAR (dysphonia, dysarthria, dysphagia)
- TRUNKAL (head drop, no sit ups)
- UPPER AIRWAY (dyspnea on exertion, orthopnea, disordered sleep)
myopathy characteristics:
- symmetric/asymmetric?
- acute/subacute/chronic?
- motor or sensory?
- proximal/distal?
- peripheral nerve/nerve root?
- musculature it affects?
myopathy characteristics
- symmetric
- subacute (weeks-months) or chronic (months-years)
- motor
- proximal usually
- NO correspondence to peripheral nerve/nerve root
- cranial, appendicular, axial musculature
- usually skeletal muscle, but can affect smooth
occasionally, myopathies present with symptoms of __________
occasionally, myopathies present with symptoms of FAILED MUSCLE RELAXATION
- stiffness
- exercise intolerance
- exertional myalgia
steps to identify the exact myopathy
1) clinical context:
- look at pattern of weakness, other features
2) blood testing
- CK, autoantibodies
3) EMG:
- presence/absence of spontaneous activity (exp. myotonic discharges)
4) muscle biopsy
5) MRI (CT is not helpful)
classifications of myopathies
ACQUIRED
- immune mediated
- infectious
- toxic/metabolic
HEREDITARY
- dystrophies
- congenital
- metabolic
- channelopathies
acquired myopathies
Immune mediated
-inflammatory, dermatomyositis, polymyositis, inclusion body myositis, necrotizing myopathy
Infectious
-HIV, influenza
Toxic/Metabolic
-steroids, immune checkpoint inhibitors
hereditary myopathies
Dystrophies
-Duchenne/Becker, FSH, myotonic
Congenital
Metabolic
-glycogen/lipid storage, mitochondrial
Channelopathies
-periodic paralysis, myotonia congenita
dermatomyositis *
- demographic
- onset
- symptoms
- weakness pattern
- associations
- diagnosis
- Tx
- any age/gender
- subacute onset
- erythematous rash
- weakness: proximal, symmetric, neck flexors, dysphagia (upper 1/3 of esophagus)
- associated with other CTD and malignancy
- diagnosis: biopsy
- Tx: immunomodulation (good outcome)
PERIVASCULAR
(mech: AutoAb against endothelial epitope causing complement-mediated small vessel injury (capillary vasculitis) = ischemic muscle death.)
inclusion body myositis *
- age
- onset
- weakness pattern
- associations
- diagnosis
- Tx
- age: >60 years
- chronic onset
- weakness: QUADRICEPS, wrist/finger flexors, dysphagia
- associated with CTD (thyroid) but not malignancy
- biopsy is diagnostic in clinical context
- Tx: immunomodulation (ineffective)
endocrine myopathy
- weakness pattern
- Diagnosis
- biopsy
- weakness: limb girdle, hip flexors
- diagnose: CK, EMG - NORMAL
- muscle biopsy: type II fiber atrophy
necrotizing myopathy
- cause
- weakness
- diagnosis
- biopsy
- toxins (statins), autoimmune, paraneoplastic
- weakness: limb girdle
- diagnosis: EMG, CK - ABNORMAL
- biopsy: myofiber necrosis
muscular dystrophies
- heritable
- progressive
- related to mutation
- biopsy associated with destructive (dystrophic) changes in muscle
- referred to by eponym or pattern of weakness
dystrophinopathies *
- Duchenne’s, Beckers
- X linked mutation of dystrophin gene (women can have less severe phenotype)
- symptomatic at 2-3, death in end of 3rd decade
- weakness: limb girdle, calf hypertrophy, tight heel cords
- associated cardiomyopathy, ventilatory muscle weakness, intellectual impairment
- dx: clinical, genetic
