Editing Muscular dystrophy (section)

{{Short description|Diseases in which skeletal and visceral muscles breaks down over time}}
{{Infobox medical condition (new)
| name            = Muscular dystrophy
| image           = MuscularDystrophy.png
| caption         = In affected muscle (right), the tissue has become disorganized and the concentration of [[dystrophin]] (green) is greatly reduced, compared to normal muscle (left).
| field           = [[Neuromuscular disorders|Neuromuscular medicine]]
| symptoms        = Increasing weakening, breakdown of [[skeletal muscles]], trouble walking<ref name=NIH2016/><ref name=NIH2016Re/>
| complications   =
| onset           =
| duration        = Chronic<ref name=NIH2016/>
| types           = > 30, including [[Duchenne muscular dystrophy]], [[Becker muscular dystrophy]], [[facioscapulohumeral muscular dystrophy]], [[limb–girdle muscular dystrophy]], [[myotonic dystrophy]]<ref name=NIH2016/><ref name=NIH2016Re/>
| causes          = [[Genetics|Genetic]] ([[X-linked recessive]], [[autosomal recessive]], or [[autosomal dominant]])<ref name=NIH2016Re/>
| risks           =
| diagnosis       = [[Genetic testing]]<ref name=NIH2016Re/>
| differential    =
| prevention      =
| treatment       = [[Pharmacotherapy]], [[physical therapy]], [[orthopedic brace|braces]], corrective [[surgery]], [[assisted ventilation]]<ref name=NIH2016/><ref name=NIH2016Re/>
| medication      =
| prognosis       = Depends on the particular disorder<ref name=NIH2016/>
| frequency       =
| deaths          =
}}
<!-- Definition and symptoms -->
'''Muscular dystrophies''' ('''MD''') are a genetically and clinically heterogeneous group of rare [[neuromuscular disease]]s that cause progressive weakness and breakdown of [[skeletal muscles]] over time.<ref name=NIH2016/> The disorders differ as to which muscles are primarily affected, the degree of weakness, how fast they worsen, and when symptoms begin.<ref name=NIH2016/> Some types are also associated with problems in other [[human organs|organs]].<ref name="NIH2016Re">{{cite web|date=March 4, 2016|title=Muscular Dystrophy: Hope Through Research|url=http://www.ninds.nih.gov/disorders/md/detail_md.htm#180483171|url-status=dead|archive-url=https://web.archive.org/web/20160930165657/http://www.ninds.nih.gov/disorders/md/detail_md.htm#180483171|archive-date=30 September 2016|access-date=12 September 2016|website=NINDS}}</ref><!-- Other symptoms include...  lung weakness, and cardiomyopathy -->

<!-- Cause and diagnosis -->
Over 30 different disorders are classified as muscular dystrophies.<ref name=NIH2016/><ref name=NIH2016Re/> Of those, [[Duchenne muscular dystrophy]] (DMD) accounts for approximately 50% of cases and affects males beginning around the age of four.<ref name=NIH2016/> Other relatively common muscular dystrophies include [[Becker muscular dystrophy]], [[facioscapulohumeral muscular dystrophy]], and [[myotonic dystrophy]],<ref name=NIH2016/> whereas [[limb–girdle muscular dystrophy]] and [[congenital muscular dystrophy]] are themselves groups of several – usually extremely rare – genetic disorders.

Muscular dystrophies are caused by [[mutation]]s in [[gene]]s, usually those involved in making muscle proteins.<ref name="NIH2016Re" /> The muscle protein, dystrophin, is in most muscle cells and works to strengthen the muscle fibers and protect them from injury as muscles contract and relax.<ref>{{Cite book |title=Comprehensive Physiology |date=2011-01-17 |publisher=Wiley |isbn=978-0-470-65071-4 |editor-last=Terjung |editor-first=Ronald |edition=1 |language=en |doi=10.1002/cphy.c140048 |pmc=4767260 |pmid=26140716 |last1=Gao |first1=Q. Q. |last2=McNally |first2=E. M. |volume=5 |issue=3 |pages=1223–1239 }}</ref> It links the muscle membrane to the thin muscular filaments within the cell. Dystrophin is an integral part of the muscular structure. An absence of dystrophin can cause impairments: healthy muscle tissue can be replaced by fibrous tissue and fat, causing an inability to generate force.<ref>{{Cite journal |last1=Gao |first1=Quan Q. |last2=McNally |first2=Elizabeth M. |date=2015-06-24 |title=The Dystrophin Complex: Structure, Function, and Implications for Therapy |url=http://dx.doi.org/10.1002/cphy.c140048 |journal=Comprehensive Physiology |volume=5 |issue=3 |pages=1223–1239 |doi=10.1002/cphy.c140048 |pmc=4767260 |pmid=26140716|isbn=9780470650714 }}</ref> Respiratory and cardiac complications can occur as well. These mutations are either [[Heredity|inherited from parents]] or may occur [[De novo mutation|spontaneously]] during [[human embryogenesis|early development]].<ref name="NIH2016Re" /> Muscular dystrophies may be [[X-linked recessive]], [[autosomal recessive]], or [[autosomal dominant]].<ref name="NIH2016Re" /> Diagnosis often involves [[blood tests]] and [[genetic testing]].<ref name="NIH2016Re" />

<!-- Treatment and prognosis -->
There is no cure for any disorder from the muscular dystrophy group.<ref name="NIH2016" /> Several drugs designed to address the root cause are currently available including [[gene therapy]] ([[Delandistrogene moxeparvovec|Elevidys]]), and [[Antisense therapy|antisense drugs]] ([[Ataluren]], [[Eteplirsen]] etc.).<ref name="NIH2016Re" /> Other medications used include [[glucocorticoid]]s ([[Deflazacort]], [[Vamorolone]]); [[calcium channel blockers]] ([[Diltiazem]]); to slow skeletal and cardiac muscle degeneration, [[anticonvulsants]] to control [[seizure]]s and some muscle activity, and [[Histone deacetylase inhibitor]]s ([[Givinostat]]) to delay damage to dying [[muscle cell]]s.<ref name="NIH2016" /> [[Physical therapy]], [[orthopedic brace|braces]], and corrective [[surgery]] may help with some symptoms<ref name="NIH2016" /> while [[assisted ventilation]] may be required in those with weakness of [[breathing muscles]].<ref name="NIH2016Re" />

Outcomes depend on the specific type of disorder.<ref name=NIH2016>{{cite web|title=NINDS Muscular Dystrophy Information Page|url=http://www.ninds.nih.gov/disorders/md/md.htm|website=NINDS|access-date=12 September 2016|date=March 4, 2016|url-status=dead|archive-url=https://web.archive.org/web/20160730004520/http://www.ninds.nih.gov/disorders/md/md.htm|archive-date=30 July 2016}}</ref> Many affected people will eventually become unable to walk<ref name=NIH2016Re/> and Duchenne muscular dystrophy in particular is associated with shortened life expectancy.

<!-- Epidemiology, history, and culture -->Muscular dystrophy was first described in the 1830s by [[Charles Bell]].<ref name="NIH2016Re" /> The word "dystrophy" comes from the Greek ''dys'', meaning "no, un-" and ''troph-'' meaning "nourish".<ref name="NIH2016Re" />