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There are seven types of congenital myopathy, which means the condition is present at birth or develops during infancy.*
*Source: National Institute of Neurological Disorders and Stroke

Myopathy Overview

Myopathy is the medical term for a muscular disorder; the plural is myopathies. The condition affects skeletal muscles, those that are connected to bones. Examples are the quadriceps muscle in the thigh and the biceps in the arm. The primary symptom of myopathy is muscle weakness.


Myopathies can be caused by genetic defects or endocrine or metabolic disorders. Other causes are infection, muscle injury, medication, problems with electrolyte levels and thyroid disease. The cause of inflammatory myopathies (see below) is not known.


Some myopathies are resistant to treatment, while others are more treatable. Myopathy can be inherited (such as the familiar muscular dystrophies) or acquired (such as common muscle cramps). In severe cases the muscle weakness can lead to respiratory failure and death.


Myopathies are categorized as follows:


  • Congenital. Developmental delays in motor skills; skeletal and facial abnormalities sometimes evident at birth. Includes central core disease.
  • Muscular. Progressive weakness in voluntary muscles; sometimes evident at birth.
  • Mitochondrial. Caused by genetic abnormalities in mitochondria, which are the structures in cells that control energy. Includes Kearns-Sayre syndrome, MELAS and MERRF.
  • Glycogen storage diseases of muscle. Caused by mutations in genes controlling enzymes that metabolize blood sugar. Includes Pompe’s, Andersen’s and Cori’s diseases.
  • Myoglobinurias. Caused by disorders in the metabolism of a fuel (myoglobin) necessary for muscle activity. Includes McArdle, Tarui and DiMauro diseases.
  • Dermatomyositis. An inflammatory condition of skin and muscle; causes a rash and in some cases cough/shortness of breath.
  • Myositis ossificans. Characterized by bone growing in muscle tissue.
  • Familial periodic paralysis. Episodes of weakness in the arms and legs.
  • Polymyositis, inclusion body myositis (IBM) and others. These are inflammatory myopathies affecting skeletal muscle.
  • Neuromyotonia. Characterized by alternating episodes of twitching and stiffness.
  • Stiff-man syndrome: Episodes of rigidity and reflex spasms.
  • Common muscle cramps and stiffness.
  • Tetany. Characterized by prlonged spasms of the arms and legs.

If you believe you may have one of these conditions make an appointment to see your WellStar neurologist to ensure effective diagnosis and treatment. Our neuroscience team is expert in helping patients diagnose, treat and live with myopathy.


Symptoms

Most myopathies result in weakening and atrophy of the muscles, especially the proximal muscles--those closest to the center of the body. The distal muscles, those farther away from the center such as in the hands or feet, are not typically affected. Individuals with myopathy often have difficulty performing activities of daily living (like dressing and bathing). Muscle pain and tenderness are rare.


Specific symptoms differ according to the type of myopathy involved. In addition to muscle weakness, many patients experience cramps and fatigue with exertion. They may have difficulty getting out of a chair, climbing stairs, changing a light bulb or washing/combing their hair. In some metabolic myopathies patients may experience tea- or dark-colored urine.


The onset and nature of symptoms can be important clues that help your physician make an accurate diagnosis. For example, if weakness progresses over hours the diagnosis may be episodic paralysis. However, if symptoms develop over a period of weeks, the condition may by polymyositis, a myopathy that can caused by medications or endocrine problems like an overly active, or underactive thyroid.


Risk Factors

Some myopathies, including some muscular dystrophy conditions, are inherited. Other risk factors for myopathy include:


  • Autoimmune disorders (myasthenia gravis, scleroderma, thyroiditis)
  • Endocrine disorders (Addison disease, Cushing syndrome, hypothyroidism, hyperthyroidism)
  • Exposure to toxins including insecticides and flame-retardant chemicals
  • Infections
  • Vitamin deficiency
  • Use of medications including antihistamines and long-term corticosteroids
  • Metabolic disorders (glycogen and lipid storage conditions)