Misplaced Pages

Revision as of 14:21, 28 June 2009

Myopathy
Specialty	Rheumatology

In medicine, a myopathy is a muscular disease in which the muscle fibers do not function for any one of many reasons, resulting in muscular weakness. "Myopathy" simply means muscle disease (myo- Greek μυσ "muscle" + -pathy Greek "suffering"). This meaning 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.

Muscular disease can be classified as neuromuscular or musculoskeletal in nature.

Some conditions, such as myositis, can be considered both neuromuscular and musculoskeletal.

Classes

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

• (G71.0) Dystrophies (or muscular dystrophies) are a subgroup of myopathies characterized by muscle degeneration and regeneration. Clinically, muscular dystrophies are typically progressive, because the muscles' ability to regenerate is eventually lost, leading to progressive weakness, often leading to use of a wheelchair, and eventually death, usually related to respiratory weakness.
  • Examples include duchenne muscular dystrophy, an x-linked condition affecting the dystrophin gene (Xp 21). Duchenne muscular dystrophy is characterised by promixal muscle weakness, seen most commonly by difficulty walking, using Gowers' sign to stand, and hypertrophy of the calf muscles. It is typically found around the age of 4, and sufferers are wheelchair bound by the age of 10. It severely limits lifespan, as most patients die in their early twenties of respiratory complications.
  • other congential muscular dystrophies include - Limb-girdle dystrophy, myotonic dystrophy, fascio-scapular-humeral dystrophy, and distal.
• (G71.1) Myotonia
  • Neuromyotonia
• (G71.2) The congenital myopathies do not show evidence for either a progressive dystrophic process (i.e., muscle death) or inflammation, 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 presence 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 myopathy) (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, which is inherited as an X-linked genetic trait, and can cause severe respiratory muscle weakness. This is the form of centronuclear myopathy currently referred to as myotubular myopathy.
    • A less severe form of centronuclear myopathy that may present itself 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 centronuclear myopathy first appears during the second 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 inflammation 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)
  • Dermatomyositisis the same as polymyositis, but also shows skin changes - a violaceous periorbital rash, facial erythema, blue or red patches on the knuckles, ragged nail folds and dilated nail capilliaries. (M33.2)
  • polymyositis which has tender, weak muscles, a mild normocytic anaemia, raised creatinine kinase and inflammatory markers and shows short polyphasic action potentials on EMG. it is treated by immunosuppressants like corticosteroids or azathioprine.
  • 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

Treatments

Because different types of myopathies are caused by many different pathways, there is no single treatment for myopathy. Treatments range from treatment of the symptoms to very specific cause-targeting treatments. Drug therapy, physical therapy, bracing for support, surgery, and even acupuncture are current treatments for a variety of myopathies.

References

1. "Myopathy - Definition from the Merriam-Webster Online Dictionary".

• Muscular disorders