In medicine, myopathy is a disease of the

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

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 Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a b ...

, 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. 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,

, and

tetany Tetany or tetanic seizure is a medical sign consisting of the involuntary contraction of muscles, which may be caused by disorders that increase the action potential frequency of muscle cells or the nerves that innervate them. Muscle cramps cause ...

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, 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. There are many types of myopathy.

ICD-10 ICD-10 is the 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD), a medical classification list by the World Health Organization (WHO). It contains codes for diseases, signs and symptoms, ...

codes are provided here where available.

Inherited forms

* (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. * (G71.1)

Myotonia Myotonia is a symptom of a small handful of certain neuromuscular disorders characterized by delayed relaxation (prolonged contraction) of the skeletal muscles after voluntary contraction or electrical stimulation. Myotonia is the defining sympt ...

Neuromyotonia Neuromyotonia (NMT) is a form of peripheral nerve hyperexcitability that causes spontaneous muscular activity resulting from repetitive motor unit action potentials of peripheral origin. NMT along with Morvan's syndrome are the most severe types i ...

* (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. Congenital myopathies include, but are not limited to: ** (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), a rare muscle wasting disorder * (G71.3) Mitochondrial myopathies, which are due to defects in

mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...

, which provide a critical source of energy for muscle * (G72.3) Familial periodic paralysis * (G72.4)

Inflammatory myopathies Inflammatory myopathy is disease featuring weakness and inflammation of muscles and (in some types) muscle pain. The cause of much inflammatory myopathy is unknown (idiopathic), and such cases are classified according to their symptoms and medical ...

, which 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, which result from defects in biochemical metabolism that primarily affect muscle ** (G73.6/E74.0)

Glycogen storage disease A glycogen storage disease (GSD, also glycogenosis and dextrinosis) is a metabolic disorder caused by an enzyme deficiency affecting glycogen synthesis, glycogen breakdown, or glucose breakdown, typically in muscles and/or liver cells. GSD has ...

s, which may affect muscle ** (G73.6/E75)

Lipid storage disorder A lipid storage disorder (or lipidosis) is any one of a group of inherited metabolic disorders in which harmful amounts of fats or lipids accumulate in some body cells and tissues. People with these disorders either do not produce enough of one ...

* (G72.89) Other myopathies **

Brody myopathy Brody myopathy, also called Brody disease, is a rare disorder that affects skeletal muscle function. BD was first characterized in 1969 by Dr. Irwin A. Brody at Duke University Medical Center. Individuals with BD have difficulty relaxing their musc ...

Congenital myopathy with abnormal subcellular organelles A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can r ...

Fingerprint body myopathy A fingerprint is an impression left by the friction ridges of a human finger. The recovery of partial fingerprints from a crime scene is an important method of forensic science. Moisture and grease on a finger result in fingerprints on surfac ...

Inclusion body myopathy 2 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 ...

** Megaconial myopathy **

Myofibrillar myopathy In medicine, myopathy is a disease of the muscle 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 meani ...

** Rimmed vacuolar myopathy

Acquired

* (G72.0 - G72.2) External substance induced myopathy ** (G72.0) Drug-induced myopathy *** Glucocorticoid myopathy is caused by this class of steroids increasing the breakdown of the muscle proteins leading to

muscle atrophy Muscle atrophy is the loss of skeletal muscle mass. It can be caused by immobility, aging, malnutrition, medications, or a wide range of injuries or diseases that impact the musculoskeletal or nervous system. Muscle atrophy leads to muscle weakness ...

. ** (G72.1) Alcoholic myopathy ** (G72.2) Myopathy due to other toxic agents - including atypical myopathy in

horses The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...

caused by toxins in sycamore seeds and seedlings. * (M33.0-M33.1) ** Dermatomyositis produces muscle weakness and skin changes. The skin rash is reddish and most commonly occurs on the face, especially around the eyes, and over the knuckles and elbows. Ragged nail folds with visible capillaries can be present. It can often be treated by drugs like corticosteroids or immunosuppressants. (M33.2) ** Polymyositis produces muscle weakness. It can often be treated by drugs like corticosteroids or immunosuppressants. **

Inclusion body myositis Inclusion body myositis (IBM) () (sometimes called sporadic inclusion body myositis, sIBM) is the most common inflammatory muscle disease in older adults. The disease is characterized by slowly progressive weakness and wasting of both proximal ...

is a slowly progressive disease that produces weakness of hand grip and straightening of the knees. No effective treatment is known. * (M61)

Myositis ossificans Myositis ossificans comprises two syndromes characterized by heterotopic ossification (calcification) of muscle. The World Health Organization, 2020, has grouped myositis ossificans together with fibro-osseous pseudotumor of digits as a single spe ...

* (M62.89)

Rhabdomyolysis Rhabdomyolysis (also called rhabdo) is a condition in which damaged skeletal muscle breaks down rapidly. Symptoms may include muscle pains, weakness, vomiting, and confusion. There may be tea-colored urine or an irregular heartbeat. Some of th ...

and (R82.1) myoglobinurias 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. *

Statin-associated autoimmune myopathy 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 tak ...

Myocardium Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that ...
/ cardio-myopathy

* ()

Acute myocarditis Myocarditis, also known as inflammatory cardiomyopathy, is an acquired cardiomyopathy due to inflammation of the heart muscle. Symptoms can include shortness of breath, chest pain, decreased ability to exercise, and an irregular heartbeat. The ...

* ()

Myocarditis Myocarditis, also known as inflammatory cardiomyopathy, is an acquired cardiomyopathy due to inflammation of the heart muscle. Symptoms can include shortness of breath, chest pain, decreased ability to exercise, and an irregular heartbeat. The ...

in diseases classified elsewhere * ()

Cardiomyopathy 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. A ...

** () Dilated cardiomyopathy ** () Obstructive

hypertrophy cardiomyopathy Hypertrophic cardiomyopathy (HCM, or HOCM when obstructive) is a condition in which the heart becomes thickened without an obvious cause. The parts of the heart most commonly affected are the interventricular septum and the ventricles. This r ...

** () Other

hypertrophic cardiomyopathy Hypertrophic cardiomyopathy (HCM, or HOCM when obstructive) is a condition in which the heart becomes thickened without an obvious cause. The parts of the heart most commonly affected are the interventricular septum and the ventricles. This r ...

** ()

Endomyocardial Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle th ...

( eosinophilic) disease *** Eosinophilic myocarditis *** Endomyocardial (tropical) fibrosis *** Löffler's endocarditis ** ()

Endocardial fibroelastosis Endocardial fibroelastosis (EFE) is a rare heart disorder usually occurring in children two years old and younger. It may also be considered a reaction to stress, not necessarily a specific disease. It should not be confused with endomyocardial fi ...

** () Other

restrictive cardiomyopathy Restrictive cardiomyopathy (RCM) is a form of cardiomyopathy in which the walls of the heart are rigid (but not thickened). Thus the heart is restricted from stretching and filling with blood properly. It is the least common of the three original s ...

** () Alcoholic cardiomyopathy ** () Other cardiomyopathies *** Arrhythmogenic right ventricular dysplasia * ()

in diseases classified elsewhere

Differential diagnosis

At birth'' * None as systemic causes; mainly hereditary Onset in childhood * Inflammatory myopathies – dermatomyositis, polymyositis (rarely) * Infectious myopathies * Endocrine and metabolic disorders – hypokalemia, hypocalcemia, hypercalcemia Onset in adulthood * Inflammatory myopathies – polymyositis, dermatomyositis, inclusion body myositis, viral (HIV) * Infectious myopathies * Endocrine myopathies – thyroid, parathyroid, adrenal, pituitary disorders * Toxic myopathies – alcohol, corticosteroids, narcotics, colchicines, chloroquine * Critical illness myopathy * Metabolic myopathies * Paraneoplastic myopathy

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 Physical therapy (PT), also known as physiotherapy, is one of the allied health professions. It is provided by physical therapists who promote, maintain, or restore health through physical examination, diagnosis, management, prognosis, patient ...

, bracing for support,

surgery Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical specialty that uses operative manual and instrumental techniques on a person to investigate or treat a pat ...

, and massage are all current treatments for a variety of myopathies.

References

External links

GeneReviews/NCBI/NIH/UW entry on Myopathy with Deficiency of ISCU
*See http://neuromuscular.wustl.edu/ for medical descriptions. {{Authority control Muscular disorders