Myopathies Clinical Presentation
- Author: Courtney A Bethel, MD, MPH; Chief Editor: Barry E Brenner, MD, PhD, FACEP more...
Obtain the family history to determine presence of periodic paralysis or muscular dystrophy. Personal history of autoimmune disease, endocrinopathy, renal insufficiency, and/or alcoholism should be noted.
Discuss any previous episodes of severe weakness, particularly any that occurred after exercise or exposure to cold temperatures, which may indicate one of the periodic paralyses. Some patients with familial hypokalemic periodic paralysis may note that the symptoms occur after eating high-carbohydrate meals.
History of medication use is very important. Steroids, lipid lowering agents, retroviral agents, alcohol, colchicine, pentachlorophenol (PCP), heroin, and a myriad of other medications may cause myopathies. In some cases, the combination of multiple myopathic agents is responsible for the acute deterioration.
Occupational and travel history may lead a physician to consider ingestion of barium chloride or carbonate as a cause for acute hypokalemic paralysis. Note the following:
These are absorbable salts (in contrast to nonabsorbable, safe, widely used barium sulfate) that may contaminate table salt or flour. Absorbable salts may be used industrially for glazing pottery.
Paralysis results when passive efflux of potassium is blocked at the cell membrane and elevated intracellular potassium decreases the resting membrane potential.
Symptoms noted generally include the following:
Symmetric proximal muscle weakness
Patient may note dark colored urine and/or fever.
No sensory complaints or paresthesias are noted with myopathies.
Atrophy and hyporeflexia are very late findings in most patients with myopathy. The early presence of these findings usually implicates neuropathies.
Significant muscle pain and tenderness without weakness should prompt physicians to consider other causes.
Acuity of symptom onset aids in diagnosis, as follows:
Weakness progressing over hours suggests a toxic etiology or one of episodic paralyses.
Weakness developing over days suggests acute dermatomyositis or rhabdomyolysis.
Symptom development over a period of weeks suggests polymyositis, steroid myopathy, or myopathy resulting from endocrine causes (eg, hyperthyroidism, hypothyroidism).
Symptoms of the patient indicate which muscle groups are involved, as follows:
Difficulty rising from chairs, getting out of the bathtub, climbing stairs, and/or shaving or combing the hair suggests proximal muscle weakness.
Weakness of distal muscles will present with symptoms of weak grasp, handwriting problems, and walking difficulties, (eg, flapping gait).
Objective weakness, usually in a symmetric distribution of proximal muscle groups is observed. Muscle tenderness is rare; muscle mass should be normal. Atrophy is a very late sign with muscle disorders. Deep tendon reflexes (DTRs) and sensory perception should be normal. DTRs may be diminished or absent in hypokalemic paralysis.
Fever, particularly with pyomyositis or polymyositis may occur. Normal level of consciousness should be preserved.
Skin examination may reveal Gottron papules, which are pink-to-violaceous scaly areas over knuckles, elbows, and knees in dermatomyositis.
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