muscular disease; myopathy
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Etiology
- muscular dystrophies
- metabolic myopathies
- mitochondrial myopathies
- congenital myopathies
- neurologic disease & neuromuscular disorders
- inflammatory myopathies (myositis)
- connective tissue disease
- endocrine disease
- infections
- drug induced myopathy
- anti-hyperlipidemic agents
- immune-mediated necrotizing myopathy (statin myopathy)
- increased risk when combined with fibrate
- ezetimibe
- nutriceuticals (red yeast rice)
- immune-mediated necrotizing myopathy (statin myopathy)
- antiviral agents
- emetics
- immunosuppressants
- microtubule inhibitors
- antimalarial agents
- alcoholism
- anti-hyperlipidemic agents
Clinical manifestations
- generally painless
- painful myopathy should prompt search for metabolic, toxic & infectious causes[1]
- progressive symmetric weakness of proximal muscles, generally of limbs
- no sensory loss
- normal reflexes
Laboratory
- elevated serum creatine kinase
- useful for monitoring disease activity & response to treatment
- levels may be normal in patients with slowly progressive myopathy
- always check serum TSH when evaluating myopathy
- genetic testing as indicated
Diagnostic procedures
- electromyography confirms myopathic changes[1]
- low amplitude, short duration, & polyphasic motor unit potentials[1]
- muscle biopsy
Differential diagnosis
- myopathy of hypothyroidism
- diffuse myalgia, proximal muscle weakness, elevation of serum creatine kinase, delayed relaxation of deep tendon reflex
- myopathy of hyperthyroidism
- brisk reflexes, fasciculations, opthalmoplegia
- myopathy of vitamin D deficiency
- proximal muscle weakness, myalgia, fatigue, osteomalacia-related bone pain
- myopathy of glucocorticoids
- proximal muscle weakness, myalgia, normal serum creatine kinase, normal EMG
- statin myopathy*
- subacute toxic myopathy, rhabdomyolysis
- risk of myopathy increased with co-administration of fibrate & CYP3A4 inhibitor
- myotonic dystrophy
- myotonia (delayed handgrip release), distal muscle weakness
* lipophilic statins (atorvastatin, simvastatin, lovastatin) more likely to cause statin myopathy than hydrophilic statins (rosuvastatin, pravastatin, fluvastatin)
More general terms
More specific terms
- eventration of diaphragm
- genetic disease of muscle (inherited myopathy)
- hyperCKemia (elevated serum creatine phosphokinase)
- malignant hyperthermia/hyperthermia of anesthesia
- metabolic myopathy
- muscle atrophy (amyotrophy)
- myasthenic syndrome (congenital myasthenic syndrome, CMS)
- myofascial pain syndrome
- myofibrillar myopathy
- myositis (inflammatory myopathy)
- myositis ossificans
- myotonic disorder
- neurogenic scapuloperoneal syndrome Kaeser type (Kaeser syndrome)
- neuromuscular disease; myoneural disease
- rhabdomyolysis
- rippling muscle disease
- sarcopenia
- toxic myopathy; drug-induced myopathy