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
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
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
- muscle biopsy: type II fiber atrophy
necrotizing myopathy
- cause
- weakness
- diagnosis
- biopsy
- toxins (statins), autoimmune, paraneoplastic
- weakness: limb girdle
- diagnosis: EMG, CK
- 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)
- weakness: limb girdle, calf hypertrophy, tight heel cords
- associated cardiomyopathy, ventilatory muscle weakness, intellectual impairment
- diagnosis: clinical, genetic
fascioscapularhumeral muscular dystrophy
- autosomal dominant
- weakness most prominent in face, scapular fixators, biceps/triceps, foot dorsiflexors
- scapular winging occurs
- diagnosis: clinical, genetic
myotonic muscular dystrophy
- autosomal dominant inheritance
- variable age of onset
- variable severity
- associated myotonia
- systemic features: cardiac conduction defects, cataracts, smooth muscle involvement, frontal balding
- diagnosis: clinical, EMG, genetic
congenital myopathy
- heritable
- not always evident at birth
- progresses slowly
- X linked
- associated dysmorphic, orthopedic features
- diagnosis: genetic, biopsy
glycogen storage disease - Pompe
- alpha glucosidase deficiency
- AR inheritance
- onset at birth
- weakness: limb, girdle, ventilatory
- associated with cardiac, liver problems
- diagnosis: slood spot, genetic
glycogen storage disease - McArdle
- myophosphorylase deficiency
- AR inheritance
- onset in childhood
- exertional muscle pain, cramping, myoglobinuria
- diagnosis: forearm exercise, genetic
lipid storage disease
- many enzymatic mutations
- depends on enzyme involved
- other end organs may be involved
- symptoms precipitated by fasting, pregnancy, or intercurrent illness
mitochondrial muscular dystrophy
- variable phenotype
- involves multiple end organs (esp those with high energy requirements)
