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Excerpt from Myopathies


Synonyms, Key Words, and Related Terms: disorder of skeletal muscle, myonosus, sarcoidosis, polymyositis, dermatomyositis, idiopathic myopathies, connective tissue disease, systemic lupus erythematosus, SLE, rheumatoid arthritis, RA, polyarteritis nodosa, acute alcoholic myopathy, drug-induced myopathy, thyrotoxic periodic paralysis, Conn syndrome, primary hyperaldosteronism, muscular dystrophy

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Background

Myopathy is a muscle disease unrelated to any disorder of innervation or neuromuscular junction. Etiologies vary widely. The common symptoms are muscle weakness, impaired function in activities of daily life, and, rarely, muscle pain and tenderness. Presence of discolored or dark urine suggests myoglobinuria.

For the emergency physician, it is important to distinguish neurologic from muscular dysfunction. However, in the face of profound weakness, establishing ABCs with attention to airway and aspiration precautions and providing supportive care are indicated while inpatient consultation and detailed studies are performed.

Pathophysiology

Most congenital myopathies or inherited myopathies are chronic slowly progressive diseases. The emergency physician rarely attends to a patient specifically to treat congenital myopathy unless acute deterioration occurs. Emergency physicians attend to patients with metabolic, inflammatory, endocrine, and toxic causes of myopathy more often than those with congenital causes because of the acute or subacute onset of symptoms associated with noncongenital forms.

Periodic paralyses are a group of diseases that cause patients to present with acute weakness due to potassium shifts, leading to muscle dysfunction. A genetic defect of the sodium ion channel in muscle cell membranes is responsible for the paralysis, which may last from hours to days.

Mortality/Morbidity

  • Morbidity and mortality of myopathies is related to the etiology of the condition, severity of disease, and the presence of comorbid conditions.
  • Severe weakness may lead to respiratory failure and death.

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