Myopathies Clinical Presentation

Updated: Jul 08, 2022
  • Author: Courtney A Bethel, MD, MPH; Chief Editor: Barry E Brenner, MD, PhD, FACEP  more...
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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, [11] 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. [12]  A prospective study of 1111 consecutive patients with muscular side effects on statin monotherapy who were admitted from a large lipidology outpatient unit over a 4-year period found that physical activity appeared to be a key trigger for statin-induced muscular side effects. [13]  Symptoms could be symmetrical, asymmetrical, generalized, or in isolated muscle groups only. [13]

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
  • Malaise
  • Fatigue
  • Patient may note dark-colored urine, fever, or both.
  • 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)

Physical Examination

Closely monitor the patient's airway if the respiratory muscles are involved.

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 may occur, particularly with pyomyositis or polymyositis. 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.