Myopathy

In medicine, a myopathy is a neuromuscular disease in which the muscle fibers dysfunction for any one of many reasons, resulting in muscular weakness. "Myopathy" simply means disorder ("pathy" from pathology) of muscle ("myo"). This implies that the primary defect is within the muscle, as opposed to the nerves ("neuropathies" or "neurogenic" disorders) or elsewhere (e.g., the brain etc.). Muscle cramps, stiffness, and spasm can also be associated with myopathy. more...

Classes

Because myopathy is such a general term, there are several classes of myopathy. (ICD-10 codes are provided where available.)

• (G71.0) "Dystrophies" ("muscular dystrophies") are a subgroup of myopathies characterized by muscle degeneration and regeneration. Clinically, muscular dystrophies are typically progressive, since the muscles ability to regenerate is eventually lost, leading to progressive weakness, often leading to confinement to a wheelchair, and eventually death, usually related to respiratory insuficiency (i.e., weak breathing).
• (G71.1) Myotonia
  • Neuromyotonia
• (G71.2) The congenital myopathies do not show evidence for either a progressive dystrophic process (i.e., muscle death) or inflamation, but instead characteristic microscopic changes are seen in association with reduced contractile ability of the muscles. Among others, different congenital myopathies include:
  • (G71.2) "nemaline myopathy" (characterized by pressense of "nemaline rods" in the muscle),
  • (G71.2) multi/minicore myopathy (characterized by multiple small "cores" or areas of disruption in the muscle fibers),
  • (G71.2) "Centronuclear myopathy" (or "myotubular") (in which the nuclei are abnormally found in the center of the muscle fibers) is a rare muscle wasting disorder that occurs in three forms:
    • The most severe form is present at birth, inherited as an X-linked genetic trait, and presents with severe respiratory muscle weakness.
    • A less severe form of myotubular myopathy that may be present at birth or in early childhood progresses slowly and is inherited as an autosomal recessive genetic trait.
    • The least severe of the three forms of myotubular myopathy presents between the first and third decades of life and is slowly progressive; it is inherited as an autosomal dominant genetic trait.
• (G71.3) "Mitochondrial myopathies" are due to defects in mitochondria which provide a critical source of energy for muscle.
• (G72.3) Familial periodic paralysis
• (G72.4) "Inflammatory myopathies" are caused by problems with the immune system attacking components of the muscle, leading to signs of inflamation in the muscle.
• (G73.6) "Metabolic myopathies" result from defects in biochemical metabolism that primarily affect muscle
  • (G73.6/E74.0) Glycogen storage diseases may affect muscle
  • (G73.6/E75) Lipid storage disorder
• (M33.0-M33.1) Dermatomyositis, (M33.2) polymyositis, inclusion body myositis, and related myopathies
• (M61) Myositis ossificans
• (M62.89) Rhabdomyolysis and (R82.1) myoglobinurias
• Common muscle (R25.2) cramps and (M25.6) stiffness, and (R29.0) tetany

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