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
Additional terms
References
- ↑ Jump up to: 1.0 1.1 1.2 1.3 Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 17, 18. American College of Physicians, Philadelphia 1998, 2012, 2015, 2018
Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022