MYOPATHY 

Created: Monday, November 12, 2007

Clinical features of myopathy

Clinical features of myopathy:

• The hallmark symptom of myopathy (and neuromuscular disease) is weakness
• Weakness predominantly affecting proximal muscle groups (shoulder and limb girdles) is typical
• Weakness manifests itself in different ways at different ages:
  • Decreased foetal movements movements in utero
  • Floppy infant neonatally
  • Motor delay in the toddler years
  • Reduced muscle strength and power in older children and adults.
• Myalgia may occur in inflammatory myopathies
• Muscle-stretch reflexes are preserved
• Somatosensory reflexes are preserved
• Variation of strength with exercise (either increasing or decreasing) can occur:
  • Fluctuating muscle power suggests metabolic myopathy (for example McArdle disease)
  • Fatigability (or progressive weakness with exertion relieved by rest) is a feature ofmyasthenia gravis where the defect is in neuromuscular transmission.

  • History

    • Common symptoms:
      • Symmetrical proximal muscle weakness
      • Malaise
      • Fatigue
      • Absence of sensory symptoms (paraesthesia)
      • Atrophy of muscles (and reduced reflexes) occurs late with myopathies (early with neuropathy)
      • Waddling gait of DMD at age 3-6 years is typical.
    • How acute are the symptoms?
      • Weakness over hours suggests toxic cause or episodic paralysis
      • Weakness developing over days- consider dermatomyositis or rhabdomyolysis
      • Weakness over weeks suggests polymyositis, steroid myopathy, endocrine myopathy.
    • Pain and tenderness without weakness- consider other causes
    • Which muscle groups are affected?
      • Proximal muscle groups- difficulty rising from chair, climbing stairs, shaving, hair combing
      • Distal muscles- difficulty walking (flaping gait), grasping, handwriting.
    • Metabolic myopathies present with:
      • Difficulty with exercise
      • Cramps and myalgia with exercise (early withglycogen storage disorders and after prolonged exercise with lipid storage disorders)
      • Myoglobinuria
      • Progressive muscle weakness in some metabolic myopathies.
    • Past medical history:
      • Autoimmune disease
        • Systemic lupus erythematosus
        • Rheumatoid arthritis
        • Polyarteritis nodosa.
      • Endocrine disease
      • Renal disease
      • Alcoholism.
    • Family history:
      • Muscular dystrophy
      • Other relevant conditions or myopathies.
    • Medication:
      • Steroids
      • Lipid lowering drugs
      • Alcohol
      • Colchicine
      • Heroin
      • Azidothymidine
    • Occupational history:
      • Pottery industry-glazing salts can cause hypokalaemic paralysis.

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