Editing Myopathy

{{Short description|Muscular disease in which the muscle fibers do not function correctly}}
{{Use dmy dates|date=April 2022}}
{{Infobox medical condition (new)
| name          = Myopathy
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| field         = [[Rheumatology]], [[Neuromuscular medicine]]
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| synonym       = Muscle disease
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In [[medicine]], '''myopathy''' is a [[disease]] of the [[muscle]]<ref name="urlMyopathy - Definition from the Merriam-Webster Online Dictionary">{{cite web |url=http://www.merriam-webster.com/dictionary/Myopathy |title=Myopathy - Definition from the Merriam-Webster Online Dictionary }}</ref> in which the [[muscle fiber]]s do not function properly. ''Myopathy'' means '''muscle disease''' ([[Greek language|Greek]] : myo- ''muscle'' + patheia ''[[pathos|-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).

This muscular defect typically results in [[myalgia]] (muscle pain), [[muscle weakness]] (reduced muscle force), or premature [[muscle fatigue]] (initially normal, but declining muscle force). [[Muscle cramp]]s, [[stiffness]], [[spasm]], and [[Muscle contracture|contracture]] can also be associated with myopathy. Myopathy experienced over a long period (chronic) may result in the muscle becoming an abnormal size, such as [[muscle atrophy]] (abnormally small) or a [[pseudoathletic appearance]] (abnormally large).

Capture myopathy can occur in wild or captive animals, such as deer and [[kangaroos]], and leads to morbidity and mortality.<ref>{{cite journal | vauthors = Green-Barber JM, Stannard HJ, Old JM | title = A suspected case of myopathy in a free-ranging eastern grey kangaroo (''Macropus giganteus'') | journal = Australian Mammalogy | volume = 40 | pages = 122–126 | date = 2018 | doi = 10.1071/AM16054 }}</ref> It usually occurs as a result of stress and physical exertion during capture and restraint.

Muscular disease can be classified as [[Neuromuscular disease|neuromuscular]] or [[Musculoskeletal disorders|musculoskeletal]] in nature. Different myopathies may be inherited, infectious, non-communicable, or idiopathic (cause unknown). The disease may be isolated to affecting only muscle (pure myopathy), or may be part of a systemic disease as is typical in [[Mitochondrial myopathy|mitochondrial myopathies]].

==Signs and symptoms==
Common symptoms include muscle weakness, cramps, stiffness, and [[tetany (medical sign)|tetany]].{{citation needed|date=October 2020}}

== Systemic diseases ==

Myopathies in systemic disease results from several different disease processes including [[Endocrine system|endocrine]], [[Inflammation|inflammatory]], [[Paraneoplastic syndrome|paraneoplastic]], infectious, drug- and toxin-induced, critical illness myopathy, metabolic, [[collagen]] related,<ref name="pmid19557868">{{cite journal | vauthors = Voermans NC, van Alfen N, Pillen S, Lammens M, Schalkwijk J, Zwarts MJ, van Rooij IA, Hamel BC, van Engelen BG | title = Neuromuscular involvement in various types of Ehlers-Danlos syndrome | journal = Ann. Neurol. | volume = 65 | issue = 6 | pages = 687–97 | date = June 2009 | pmid = 19557868 | doi = 10.1002/ana.21643 | s2cid = 22600065 }}</ref> and myopathies with other systemic disorders. Patients with systemic myopathies often present [[Acute (medicine)|acutely]] or subacutely. On the other hand, [[Congenital myopathy|familial myopathies]] or [[Muscular dystrophy|dystrophies]] generally present in a [[Chronic condition|chronic]] fashion with exceptions of [[Metabolic myopathy|metabolic myopathies]], where symptoms on occasion can be precipitated acutely. Metabolic myopathies, which affect the production of ATP within the muscle cell, typically present with [[Signs and symptoms#Dynamic and static|dynamic]] (exercise-induced) rather than static symptoms.<ref>{{Cite journal |last1=Darras |first1=Basil T. |last2=Friedman |first2=Neil R. |date=February 2000 |title=Metabolic myopathies: a clinical approach; part I |url=https://linkinghub.elsevier.com/retrieve/pii/S0887899499001332 |journal=Pediatric Neurology |language=en |volume=22 |issue=2 |pages=87–97 |doi=10.1016/S0887-8994(99)00133-2|pmid=10738913 |url-access=subscription }}</ref> Most of the [[Inflammatory myopathy|inflammatory myopathies]] can have a chance association with malignant lesion; the incidence appears to be specifically increased only in patients with dermatomyositis.<ref name="pmid21886637">{{cite journal | vauthors = Chawla J | title = Stepwise approach to myopathy in systemic disease | journal = Front Neurol | volume = 2 | pages = 49 | date = 2011 | pmid = 21886637 | pmc = 3153853 | doi = 10.3389/fneur.2011.00049  | doi-access = free }}</ref>

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

===Inherited forms===
* (G71.0) [[muscular dystrophy|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 and often leading to use of a [[wheelchair]] and eventually death, usually related to [[respiratory]] weakness.
* (G71.1) [[Myotonia]]
** [[Neuromyotonia]]
* (G71.2) The [[congenital myopathy|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 [[cell nucleus|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]], which provide a critical source of energy for muscle
* (G72.3) Familial [[periodic paralysis]]
* (G72.4) [[inflammatory myopathy|Inflammatory myopathies]], 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 myopathy|Metabolic myopathies]], which result from defects in biochemical metabolism that primarily affect muscle
** (G73.6/E74.0) [[Glycogen storage disease]]s, which may affect muscle
** (G73.6/E75) [[Lipid storage disorder]]
* (G72.89) Other myopathies
** [[Brody myopathy]]
** [[Congenital myopathy with abnormal subcellular organelles]]
** [[Fingerprint body myopathy]]
** [[Inclusion body myopathy 2]]
** [[CHKB (gene)#Megaconial Congenital Muscular Dystrophy (MDCMC)|Megaconial myopathy]]
** [[Myofibrillar myopathy]]
** [[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 [[catabolism|increasing the breakdown]] of the muscle proteins leading to [[muscle atrophy]].<ref name="pmid8049126">{{cite journal | vauthors = Seene T | title = Turnover of skeletal muscle contractile proteins in glucocorticoid myopathy | journal = J. Steroid Biochem. Mol. Biol. | volume = 50 | issue = 1–2 | pages = 1–4 | date = July 1994 | pmid = 8049126 | doi = 10.1016/0960-0760(94)90165-1 | s2cid = 27814895 }}</ref>
** (G72.1) [[Alcoholic myopathy]]
** (G72.2) Myopathy due to other toxic agents, including [[Equine atypical myopathy|atypical myopathy]] in [[horses]] caused by toxins in [[Acer pseudoplatanus|sycamore]] seeds and seedlings.<ref>{{cite web|url=https://www.rainbowequinehospital.co.uk/information-on-sycamore-poisoning/|title=Information On Sycamore Poisoning|publisher = Rainbow Equine Hospital|access-date=16 May 2017}}</ref><ref>{{cite web|url=http://www.rvc.ac.uk/equine-vet/news/equine-atypical-myopathy-toxin-and-biochemical-tests-and-tree-sample-testing-available-at-the-royal-veterinary-college|title=Equine Atypical Myopathy toxin and biochemical tests and tree sample testing available at the RVC|publisher= Royal Veterinary college - University of London|access-date=16 May 2017|date=13 February 2017}}</ref>
* (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]] is a slowly progressive disease that produces weakness of hand grip and straightening of the knees.  No effective treatment is known.
* (M60.9) [[Benign acute childhood myositis]]
* (M61) [[Myositis ossificans]]
* (M62.89) [[Rhabdomyolysis]] and (R82.1) [[myoglobinuria]]s
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]]

===[[Myocardium]] / [[cardiomyopathy|cardiomyopathy]]===
* ({{ICD10|I|40||i|30}}) [[Acute myocarditis]]
* ({{ICD10|I|41||i|30}}) [[Myocarditis]] in diseases classified elsewhere
* ({{ICD10|I|42||i|30}}) [[Cardiomyopathy]]
** ({{ICD10|I|42|0|i|30}}) [[Dilated cardiomyopathy]]
** ({{ICD10|I|42|1|i|30}}) Obstructive [[hypertrophy cardiomyopathy]]
** ({{ICD10|I|42|2|i|30}}) Other [[hypertrophic cardiomyopathy]]
** ({{ICD10|I|42|3|i|30}}) [[Endomyocardial]] ([[eosinophilic]]) disease
*** [[Eosinophilic myocarditis]]
*** [[Endomyocardial (tropical) fibrosis]]
*** [[Löffler's endocarditis]]
** ({{ICD10|I|42|4|i|30}}) [[Endocardial fibroelastosis]]
** ({{ICD10|I|42|5|i|30}}) Other [[restrictive cardiomyopathy]]
** ({{ICD10|I|42|6|i|30}}) [[Alcoholic cardiomyopathy]]
** ({{ICD10|I|42|8|i|30}}) Other [[cardiomyopathies]]
*** [[Arrhythmogenic right ventricular dysplasia]]
* ({{ICD10|I|43||i|30}}) [[Cardiomyopathy]] in diseases classified elsewhere

<ref name="The Webs Free 2019 ICD-10-CM/PCS Medical Coding Reference 2018">{{cite web | title=2019 ICD-10-CM Diagnosis Code I42.9: Cardiomyopathy, unspecified | website=The Web's Free 2019 ICD-10-CM/PCS Medical Coding Reference | date=1 October 2018 | url=https://www.icd10data.com/ICD10CM/Codes/I00-I99/I30-I52/I42-/I42.9 | access-date=5 February 2019}}</ref>

===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'''<ref name="pmid21886637"/>
* 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]], bracing for support, [[surgery]], and massage are all current treatments for a variety of myopathies.{{citation needed|date=October 2020}}

==References==
{{Reflist}}

==External links==
* [https://www.ncbi.nlm.nih.gov/books/NBK5299/  GeneReviews/NCBI/NIH/UW entry on Myopathy with Deficiency of ISCU]
* See http://neuromuscular.wustl.edu/ for medical descriptions.

{{Diseases of myoneural junction and muscle}}
{{Systemic connective tissue disorders}}
{{Myopathy}}
{{Authority control}}

[[Category:Muscular disorders]]