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| ==Classification== | | ==Classification== |
| There is no established system for the classification of Duchenne muscular dystrophy. For more information about muscular dystrophy classification [[Muscular dystrophy|click here]]. | | There is no established system for the classification of Duchenne muscular dystrophy. For more information about muscular dystrophy classification [[Muscular dystrophy|click here]]. |
| {| class="wikitable"
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| ! Type
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| ! [[OMIM]]
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| ! Gene
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| ! Description
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| | [[Becker's muscular dystrophy]]
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| | {{OMIM2|300376}}
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| | ''[[Dystrophin|DMD]]''
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| * Becker muscular dystrophy (BMD) is a less severe variant of [[Duchenne muscular dystrophy]].
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| * It is caused by the production of a truncated, but partially functional form of [[dystrophin]].<ref name="2006 report to Congress" /> Survival is usually into old age.<ref name="MD USA WEBSITE">[http://www.mdausa.org/disease/40list.html]: MD USA Website (accessed 03SEP2007)</ref>
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| * Affects only boys (with extremely rare exceptions)
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| | [[Congenital muscular dystrophy]]
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| | Multiple
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| | Multiple
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| * Age at onset: birth; symptoms include general muscle weakness and possible joint deformities; disease progresses slowly; shortened life span.<ref>{{cite web|title=Congenital Muscular Dystrophy (CMD)|url=http://www.mdausa.org/disease/cmd.html|publisher=MDA|accessdate=27 April 2012}}</ref>
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| * Congenital muscular dystrophy includes several disorders with a range of symptoms.
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| * Muscle degeneration may be mild or severe. Problems may be restricted to skeletal muscle, or muscle degeneration may be paired with effects on the brain and other organ systems.
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| * A number of the forms of the congenital muscular dystrophies are caused by defects in proteins that are thought to have some relationship to the dystrophin-glycoprotein complex and to the connections between muscle cells and their surrounding cellular structure.
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| * Some forms of congenital muscular dystrophy show severe brain malformations, such as [[lissencephaly]] and [[hydrocephalus]].<ref name="2006 report to Congress" />
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| | [[Duchenne muscular dystrophy]]
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| | {{OMIM2|310200}}
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| | ''[[Dystrophin|DMD]]''
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| * Duchenne muscular dystrophy (DMD) is the most common childhood form of muscular dystrophy, it generally affects only boys (with extremely rare exceptions), becoming clinically evident when a child begins walking.
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| * By age 10, the child may need braces for walking and by age 12, most patients are confined to a wheelchair.<ref name="nlm.nih.gov">http://www.nlm.nih.gov/medlineplus/ency/article/000705.htm</ref>
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| * Patients usually die around age 25, but this depends from person to person.<ref name="nlm.nih.gov" />
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| * In the early 1990s, researchers identified the gene for the protein [[dystrophin]] which, when absent, causes DMD. The amount of dystrophin correlates with the severity of the disease (i.e. the less dystrophin present, the more severe the phenotype). Since the gene is on the X chromosome, this disorder affects primarily males, and females who are carriers have milder symptoms. Sporadic mutations in this gene occur frequently, accounting for a third of cases. The remaining two-thirds of cases are inherited in a recessive pattern.
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| * Dystrophin is part of a complex structure involving several other protein components. The "dystrophin-glycoprotein complex" helps anchor the structural skeleton ([[cytoskeleton]]) within the muscle cells, through the outer membrane ([[sarcolemma]]) of each cell, to the tissue framework (extracellular matrix) that surrounds each cell.
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| * Due to defects in this assembly, contraction of the muscle leads to disruption of the outer membrane of the muscle cells and eventual weakening and wasting of the muscle.<ref name="2006 report to Congress" />
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| | [[Distal muscular dystrophy]]
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| | {{OMIM2|254130}}
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| | ''[[Dysferlin|DYSF]]''
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| * Distal muscular dystrophies' age at onset: 20 to 60 years; symptoms include weakness and wasting of muscles of the hands, forearms, and lower legs; progress is slow and not life-threatening.<ref name="MD USA WEBSITE" />
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| * Miyoshi myopathy, one of the distal muscular dystrophies, causes initial weakness in the calf muscles, and is caused by defects in the same gene responsible for one form of [[Limb-girdle muscular dystrophy|LGMD (Limb Girdle Muscular Dystrophy)]].<ref name="2006 report to Congress" />
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| | [[Emery-Dreifuss muscular dystrophy]]
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| | {{OMIM2|310300}}, {{OMIM2|181350}}
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| | ''[[emerin|EMD]]'', ''[[LMNA]]''
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| * Emery-Dreifuss Muscular Dystrophy patients normally present in childhood and the early teenage years with contractures.
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| * Clinical signs include muscle weakness and wasting, starting in the distal limb muscles and progressing to involve the limb-girdle muscles. Most patients also suffer from [[cardiac conduction defects]] and [[arrhythmias]] which, if left untreated, increase the risk of [[stroke]] and sudden death.
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| * There are three subtypes of Emery-Dreifuss Muscular Dystrophy, distinguishable by their pattern of inheritance: X-Linked, autosomal dominant and autosomal recessive. The X-linked form is the most common. Each type varies in prevalence and symptoms.
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| * The disease is caused by mutations in the LMNA gene, or more commonly, the EMD gene. Both genes encode for protein componenets of the nuclear envelope. However, how the pathogenesis of these mutations is not well understood.<ref>[http://www.emedicine.com/neuro/topic513.htm Emedicine re EDMD] Retrieved 30 July 2007.</ref>
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| | [[Facioscapulohumeral muscular dystrophy]]
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| | {{OMIM2|158900}}
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| | ''[[DUX4]]''
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| * Facioscapulohumeral muscular dystrophy (FSHD) initially affects the muscles of the face, shoulders, and upper arms with progressive weakness. Symptoms usually develop in the teenage years. Some affected individuals become severely disabled.
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| * The pattern of inheritance is [[autosomal dominant]], but there are a significant number of spontaneous mutations.
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| * Seminal research published in August 2010 documents that two defects are needed for FSHD, which for the first time provides [[FSHD#A Unifying Theory|a unifying theory]] for the underlying genetics of FSHD. The first is the deletion of D4Z4 repeats and the second is a "toxic gain of function" of the [[DUX4]] gene.<ref name="2006 report to Congress" /><ref name="NYTJunkDNA">{{cite news|last=Kolata|first=Gina|title=Reanimated 'Junk' DNA Is Found to Cause Disease|url=http://www.nytimes.com/2010/08/20/science/20gene.html?_r=2&emc=eta1|accessdate=29 August 2010|newspaper=[[New York Times]]|date=19 August 2010}}</ref>
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| <ref name="Unifying">{{cite journal|last=Lemmers|first=Richard|coauthors=Patrick J. van der Vliet, Rinse Klooster, Sabrina Sacconi, Pilar Camaño, Johannes G. Dauwerse, Lauren Snider, Kirsten R. Straasheijm, Gert Jan van Ommen, George W. Padberg, Daniel G. Miller, Stephen J. Tapscott, Rabi Tawil, Rune R. Frants, and Silvère M. van der Maarel |title=A Unifying Genetic Model for Facioscapulohumeral Muscular Dystrophy|journal=Science|volume=329|issue=5999|pages=1650–3|date=19 August 2010|pmid=20724583|doi=10.1126/science.1189044|url=http://www.sciencemag.org/cgi/content/abstract/science.1189044}}</ref>
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| * Facioscapulohumeral muscular dystrophy (FSHD) occurs both in males and females.
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| | [[Limb-girdle muscular dystrophy]]
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| | Multiple
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| | Multiple
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| * Limb-girdle muscular dystrophy is also called LGMD. Affects both boys and girls. LGMDs all show a similar distribution of muscle weakness, affecting both upper arms and legs.
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| * Many forms of LGMD have been identified, showing different patterns of inheritance (autosomal recessive vs. autosomal dominant).
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| * In an autosomal recessive pattern of inheritance, an individual receives two copies of the defective gene, one from each parent. The recessive LGMDs are more frequent than the dominant forms, and usually have childhood or teenage onset. The dominant LGMDs usually show adult onset. Some of the recessive forms have been associated with defects in proteins that make up the dystrophin-glycoprotein complex.<ref name="2006 report to Congress" />
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| * Though a person normally leads a normal life with some assistance, in some extreme cases, death from LGMD occurs due to cardiopulmonary complications.<ref>{{cite book|last=Jenkins|first=Simon P.R.|title=Sports Science Handbook:I - Z.|year=2005|publisher=Multi-Science Publ. Co.|location=Brentwood, Essex|isbn=0906522-37-4|pages=121}}</ref>
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| | [[Myotonic muscular dystrophy]]
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| | {{OMIM2|160900}}, {{OMIM2|602668}}
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| | ''[[Myotonin-protein kinase|DMPK]]'', ''[[ZNF9]]''
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| * Myotonic muscular dystrophy is an autosomal dominant condition that presents with [[myotonia]] (delayed relaxation of muscles) as well as muscle wasting and weakness.<ref name="Turner">{{cite journal|last=Turner|first=C|coauthors=Hilton-Jones D.|title=The myotonic dystrophies: diagnosis and management|journal=J Neurol Neurosurg Psychiatry|year=2010|volume=81|pages=358–367|doi=10.1136/jnnp.2008.158261|pmid=20176601|url=http://jnnp.bmj.com/content/81/4/358.long}}</ref> * Myotonic dystrophy varies in severity and manifestations and affects many body systems in addition to skeletal muscles, including the heart, endocrine organs, eyes, and gastrointestinal tract.
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| * Myotonic muscular dystrophy type 1 (DM1), also known as Steinert disease, is the most common adult form of muscular dystrophy. It results from the expansion of a short (CTG) repeat in the DNA sequence of the DMPK (myotonic dystrophy protein kinase) gene.
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| * Myotonic muscular dystrophy type 2 (DM2) is much rarer and is a result of the expansion of the CCTG repeat in the ZNF9 (zinc finger protein 9) gene. While the exact mechanisms of action are not known, these molecular changes may interfere with the production of important muscle proteins.<ref name="2006 report to Congress" />
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| | [[Oculopharyngeal muscular dystrophy]]
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| | {{OMIM2|164300}}
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| | ''[[PABPN1]]''
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| * Oculopharyngeal MD's age at onset: 40 to 70 years.
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| * Symptoms affect muscles of eyelids, face, and throat followed by pelvic and shoulder muscle weakness, has been attributed to a short repeat expansion in the [[genome]] which regulates the translation of some genes into functional proteins.<ref name="2006 report to Congress" />
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| According to the functional Classification System for DMD (AFCSD), there are 5 stages of Duchenne muscular dystrophy based on the gross Motor Function. | | According to the functional Classification System for DMD (AFCSD), there are 5 stages of Duchenne muscular dystrophy based on the gross Motor Function. |