Steroid induced: etiology includes long term glucocorticoid use, cushings disease
Statin induced: symptoms include vague ache more than weakness; can occur at any time, rarely rhabdomyolysis
Other medication/drugs induced muscle breakdown: neuroleptic malignant syndrome, malignant hyperthermia, serotonin syndrome; some drugs of abuse
Alcohol induced muscle weakness
Trauma induced rhabdomyolysis: This is typically related to significant crush or other injury to muscles, with obvious findings and history (careful exam in those who present w/altered mental status); also with long periods of immobility/lying on the ground (e.g. after syncope or stroke where patient can't move and no help available); compartment syndrome; severe forms of exercise can sometimes precipitate rhabdomyolysis
Low phosphorous levels
Glycogen storage disorder--> very uncommon
Symptoms
May be related to underlying disease
Muscular weakness and fatigue
As symptoms progress, can have inability to perform ADLs, walk
Dysphagia and SOB if muscles of respiration and swallowing affected.
Physical Exam Findings
Overt weakness in affected muscles
Sensory testing may be normal
May have other findings related to underlying process
May have atrophy of affected muscles (if long standing)