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Specialty Rheumatology

In medicine, myopathy is a disease of the muscle [1] in which the muscle fibers do not function properly. This results in muscular weakness. Myopathy means muscle disease (Greek  : myo- muscle + patheia -pathy  : 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). Muscle cramps, stiffness, and spasm can also be associated with myopathy.


Capture myopathy can occur in wild or captive animals, such as deer and kangaroos, and leads to morbidity and mortality. [2] It usually occurs as a result of stress and physical exertion during capture and restraint.

Muscular disease can be classified as neuromuscular or musculoskeletal in nature. Some conditions, such as myositis, can be considered both neuromuscular and musculoskeletal.

Signs and symptoms

Common symptoms include muscle weakness, cramps, stiffness, and tetany.[ citation needed ]

Systemic diseases

Myopathies in systemic disease results from several different disease processes including endocrine, inflammatory, paraneoplastic, infectious, drug- and toxin-induced, critical illness myopathy, metabolic, collagen related, [3] and myopathies with other systemic disorders. Patients with systemic myopathies often present acutely or sub acutely. On the other hand, familial myopathies or dystrophies generally present in a chronic fashion with exceptions of metabolic myopathies where symptoms on occasion can be precipitated acutely. Most of the inflammatory myopathies can have a chance association with malignant lesion; the incidence appears to be specifically increased only in patients with dermatomyositis. [4]

There are many types of myopathy. ICD-10 codes are provided here where available.

Inherited forms


The Food and Drug Administration is recommending that physicians restrict prescribing high-dose Simvastatin (Zocor, Merck) to patients, given an increased risk of muscle damage. The FDA drug safety communication stated that physicians should limit using the 80-mg dose unless the patient has already been taking the drug for 12 months and there is no evidence of myopathy. "Simvastatin 80 mg should not be started in new patients, including patients already taking lower doses of the drug," the agency states.

Myocardium / cardio-myopathy


Differential diagnosis

At birth

Onset in childhood

Onset in adulthood [4]


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 massage are all current treatments for a variety of myopathies.[ citation needed ]

Related Research Articles

Inclusion body myositis (IBM) is the most common inflammatory muscle disease in older adults. The disease is characterized by slowly progressive weakness and wasting of both proximal muscles and distal muscles, most apparent in the finger flexors and knee extensors. IBM is often confused with an entirely different class of diseases, called hereditary inclusion body myopathies (hIBM). The "M" in hIBM is an abbreviation for "myopathy" while the "M" in IBM is for "myositis". In IBM, two processes appear to occur in the muscles in parallel, one autoimmune and the other degenerative. Inflammation is evident from the invasion of muscle fibers by immune cells. Degeneration is characterized by the appearance of holes, deposits of abnormal proteins, and filamentous inclusions in the muscle fibers. sIBM is a rare disease, with a prevalence ranging from 1 to 71 individuals per million.

<span class="mw-page-title-main">Cardiomyopathy</span> Disease of the heart muscle

Cardiomyopathy is a group of diseases that affect the heart muscle. Early on there may be few or no symptoms. As the disease worsens, shortness of breath, feeling tired, and swelling of the legs may occur, due to the onset of heart failure. An irregular heart beat and fainting may occur. Those affected are at an increased risk of sudden cardiac death.

Myalgia is the medical term for muscle pain. Myalgia is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another likely cause is viral infection, especially when there has been no trauma.

Weakness is a symptom of a number of different conditions. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a variety of skeletal muscle diseases, including muscular dystrophy and inflammatory myopathy. It occurs in neuromuscular junction disorders, such as myasthenia gravis.

<span class="mw-page-title-main">Juvenile dermatomyositis</span> Medical condition

Juvenile dermatomyositis (JDM) is an idiopathic inflammatory myopathy (IMM) of presumed autoimmune dysfunction resulting in muscle weakness among other complications. It manifests itself in children; it is the pediatric counterpart of dermatomyositis. In JDM, the body's immune system attacks blood vessels throughout the body, causing inflammation called vasculitis. In the United States, the incidence rate of JDMS is approximately 2-3 cases per million children per year. The UK incidence is believed to be between 2-3 per million children per year, with some difference between ethnic groups. The sex ratio is approximately 2:1. Other Idiopathic inflammatory myopathies include; juvenile polymyositis (PM), which is rare and not as common in children as in adults.

<span class="mw-page-title-main">Dermatomyositis</span> Medical condition

Dermatomyositis (DM) is a long-term inflammatory disorder which affects skin and the muscles. Its symptoms are generally a skin rash and worsening muscle weakness over time. These may occur suddenly or develop over months. Other symptoms may include weight loss, fever, lung inflammation, or light sensitivity. Complications may include calcium deposits in muscles or skin.

<span class="mw-page-title-main">Polymyositis</span> Medical condition

Polymyositis (PM) is a type of chronic inflammation of the muscles related to dermatomyositis and inclusion body myositis. Its name means "inflammation of many muscles". The inflammation of polymyositis is mainly found in the endomysial layer of skeletal muscle, whereas dermatomyositis is characterized primarily by inflammation of the perimysial layer of skeletal muscles.

Hereditary inclusion body myopathies (HIBM) are a group of rare genetic disorders which have different symptoms. Generally, they are neuromuscular disorders characterized by muscle weakness developing in young adults. Hereditary inclusion body myopathies comprise both autosomal recessive and autosomal dominant muscle disorders that have a variable expression (phenotype) in individuals, but all share similar structural features in the muscles.

<span class="mw-page-title-main">Myositis</span> Medical condition

Myositis is a rare disease that involves inflammation of the muscles. This can present with a variety of symptoms such as skin involvement, muscle weakness, and other organ involvement. You can also have systemic symptoms such as weight loss, fatigue, and low fever.

<span class="mw-page-title-main">Neuromuscular disease</span> Medical condition

A neuromuscular disease is any disease affecting the peripheral nervous system (PNS), the neuromuscular junction, or skeletal muscle, all of which are components of the motor unit. Damage to any of these structures can cause muscle atrophy and weakness. Issues with sensation can also occur.

<span class="mw-page-title-main">Congenital muscular dystrophy</span> Medical condition

Congenital muscular dystrophies are autosomal recessively-inherited muscle diseases. They are a group of heterogeneous disorders characterized by muscle weakness which is present at birth and the different changes on muscle biopsy that ranges from myopathic to overtly dystrophic due to the age at which the biopsy takes place.

Mixed connective tissue disease, commonly abbreviated as MCTD, is an autoimmune disease characterized by the presence of elevated blood levels of a specific autoantibody, now called anti-U1 ribonucleoprotein (RNP) together with a mix of symptoms of systemic lupus erythematosus (SLE), scleroderma, and polymyositis. The idea behind the "mixed" disease is that this specific autoantibody is also present in other autoimmune diseases such as systemic lupus erythematosus, polymyositis, scleroderma, etc. MCTD was characterized as an individual disease in 1972 by Sharp et al., and the term was introduced by Leroy in 1980.

<span class="mw-page-title-main">Deflazacort</span>

Deflazacort is a glucocorticoid used as an anti-inflammatory and immunomodulatory agent. It was patented in 1965 and approved for medical use in 1985. The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication for Duchenne Muscular Dystrophy.

Scleromyositis, is an autoimmune disease. People with scleromyositis have symptoms of both systemic scleroderma and either polymyositis or dermatomyositis, and is therefore considered an overlap syndrome. Although it is a rare disease, it is one of the more common overlap syndromes seen in scleroderma patients, together with MCTD and Antisynthetase syndrome. Autoantibodies often found in these patients are the anti-PM/Scl (anti-exosome) antibodies.

<span class="mw-page-title-main">Inflammatory myopathy</span> Medical condition

Inflammatory myopathy is disease featuring weakness and inflammation of muscles and muscle pain. The cause of much inflammatory myopathy is unknown (idiopathic), and such cases are classified according to their symptoms and signs and electromyography, MRI and laboratory findings. It can also be associated with underlying cancer. The main classes of idiopathic inflammatory myopathy are polymyositis (PM), dermatomyositis (DM), and inclusion-body myositis (IBM).

<span class="mw-page-title-main">Camptocormia</span>

Camptocormia, also known as bent spine syndrome (BSS), is a symptom of a multitude of diseases that is most commonly seen in the elderly. It is identified by an abnormal thoracolumbar spinal flexion, which is a forward bending of the lower joints of the spine, occurring in a standing position. In order to be classified as BSS, the anterior flexion must be of 45 degrees anteriorly. This classification differentiates it from a similar syndrome known as kyphosis. Although camptocormia is a symptom of many diseases, there are two common origins: neurological and muscular. Camptocormia is treated by alleviating the underlying condition causing it through therapeutic measures or lifestyle changes.

Although they vary in particulars, polymyositis, dermatomyositis and inclusion body myositis are idiopathic inflammatory myopathies (IIM) primarily characterized by chronic inflammation of human skeletal muscle tissue that ultimately causes the necrosis of muscle cells. This degeneration leads to muscle tissue wasting, weakness and fatigue among other serious effects. Until recently, exercise has been avoided as a type of therapy, and even forbidden due to the risk of triggering or amplifying inflammation. However, several studies have been conducted to test this assumption and have shown that aerobic exercise as well as resistance training can maintain and even improve quality of life for IIM-affected individuals without increased inflammatory response.

<span class="mw-page-title-main">Acquired non-inflammatory myopathy</span> Medical condition

Acquired non-inflammatory myopathy (ANIM) is a neurological disorder primarily affecting skeletal muscle, most commonly in the limbs of humans, resulting in a weakness or dysfunction in the muscle. A myopathy refers to a problem or abnormality with the myofibrils, which compose muscle tissue. In general, non-inflammatory myopathies are a grouping of muscular diseases not induced by an autoimmune-mediated inflammatory pathway. These muscular diseases usually arise from a pathology within the muscle tissue itself rather than the nerves innervating that tissue. ANIM has a wide spectrum of causes which include drugs and toxins, nutritional imbalances, acquired metabolic dysfunctions such as an acquired defect in protein structure, and infections.

Statin-associated autoimmune myopathy (SAAM), also known as anti-HMGCR myopathy, is a very rare form of muscle damage caused by the immune system in people who take statin medications. However, there are cases of SAAM in patients who have not taken statin medication, and this can be explained by the exposure to natural sources of statin such as red yeast rice, which is statin rich. This theory is supported by the higher prevalence of statin-naive SAAM patients in Asian cohorts, who have statin-rich diets.


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  5. Seene T (July 1994). "Turnover of skeletal muscle contractile proteins in glucocorticoid myopathy". J. Steroid Biochem. Mol. Biol. 50 (1–2): 1–4. doi:10.1016/0960-0760(94)90165-1. PMID   8049126. S2CID   27814895.
  6. "Information On Sycamore Poisoning". Rainbow Equine Hospital. Retrieved 16 May 2017.
  7. "Equine Atypical Myopathy toxin and biochemical tests and tree sample testing available at the RVC". Royal Veterinary college - University of London. 13 February 2017. Retrieved 16 May 2017.
  8. "2019 ICD-10-CM Diagnosis Code I42.9: Cardiomyopathy, unspecified". The Web's Free 2019 ICD-10-CM/PCS Medical Coding Reference. 1 October 2018. Retrieved 5 February 2019.