What is Myopathy?

The myopathies are neuromuscular disorders in which the primary symptom is muscle weakness due to dysfunction of muscle fiber. Other symptoms of myopathy can include include muscle cramps, stiffness, and spasm. Myopathies can be inherited (such as the muscular dystrophies) or acquired (such as common muscle cramps). Myopathies are grouped as follows:

  • congenital myopathies: characterised by developmental delays in motor skills; skeletal and facial abnormalities are occasionally evident at birth
  • muscular dystrophies: characterised by progressive weakness in voluntary muscles; sometimes evident at birth
  • mitochondrial myopathies: caused by genetic abnormalities in mitochondria, cellular structures that control energy; include Kearns-Sayre syndrome, MELAS and MERRF
  • glycogen storage diseases of muscle: caused by mutations in genes controlling enzymes that metabolize glycogen and glucose (blood sugar); include Pompe's, Andersen's and Cori's diseases
  • myoglobinurias: caused by disorders in the metabolism of a fuel (myoglobin) necessary for muscle work; include McArdle, Tarui, and DiMauro diseases
  • dermatomyositis: an inflammatory myopathy of skin and muscle
  • myositis ossificans: characterised by bone growing in muscle tissue
  • familial periodic paralysis: characterised by episodes of weakness in the arms and legs
  • polymyositis, inclusion body myositis, and related myopathies: inflammatory myopathies of skeletal muscle
  • neuromyotonia: characterised by alternating episodes of twitching and stiffness; and
  • stiff-man syndrome:  characterised by episodes of rigidity and reflex spasms
  • common muscle cramps and stiffness, and
  • tetany:  characterised by prolonged spasms of the arms and legs

Is there any treatment?

Treatments for the myopathies depend on the disease or condition and specific causes. Supportive and symptomatic treatment may be the only treatment available or necessary for some disorders. Treatment for other disorders may include drug therapy, such as immunosuppressives, physical therapy, bracing to support weakened muscles, and surgery.

What is the prognosis?

The prognosis for individuals with a myopathy varies. Some individuals have a normal life span and little or no disability. For others, however, the disorder may be progressive, severely disabling, life-threatening, or fatal.
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