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| {{Infobox_Disease |
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| Name = {{PAGENAME}} |
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| Image = |
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| Caption = |
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| DiseasesDB = 5296 |
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| ICD10 = {{ICD10|E|74|0|e|70}} |
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| ICD9 = {{ICD9|271.0}} |
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| ICDO = |
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| OMIM = 232300 |
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| MedlinePlus = |
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| MeshID = D006009 |
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| }}
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| {{Glycogen storage disease type II}}
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| {{CMG}}
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| {{SK}} Glycogen storage disease type II; Pompe disease; acid maltase deficiency
| | '''For the main page on glycogen storage disease, please click [[Glycogen storage disease|here]]'''<br> |
| | '''For patient information click [[Glycogen storage disease type II (patient information)|here]]''' |
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| '''Glycogen storage disease type II''' (also called '''Pompe disease''' or '''acid maltase deficiency''') is a rare genetic disorder caused by a deficiency in the [[enzyme]] [[Amylase#Acid α-glucosidase|acid alpha-glucosidase]] (GAA) ({{EC number|3.2.1.20 }}), which is needed to break down [[glycogen]], a stored form of [[sugar]] used for energy. It is the only [[glycogen storage disease]] with a defect in lysosomal metabolism, and was the first [[glycogen storage disease]] to be identified—in 1932. The build-up of glycogen causes progressive muscle weakness ([[myopathy]]) throughout the body and affects various body tissues, particularly in the [[heart]], [[skeletal muscle]]s, [[liver]] and [[nervous system]]. Transmission is by autosomal recessive inheritance; therefore, children have a 1 in 4 chance of inheriting the disease when both parents carry the abnormal gene. It is estimated to occur in about 1 in 40,000-300,000 births.
| | {{Glycogen storage disease type II}} |
| | {{CMG}}; {{AE}}{{Anmol}} |
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| ==Variants==
| | {{SK}} Glycogen storage disease type 2; Pompe disease; acid maltase deficiency; glycogenosis type 2; alpha-1, 4-glucosidase deficiency; GSD II; GSD type 2; acid alpha-glucosidase deficiency; GAA deficiency; Generalized cardiac form glycogenosis; Cardiomegalia glycogenica diffusa. |
| Pompe disease has historically been divided into three forms defined by age of onset and progression of symptoms (see below). More recently there has been a trend to divide the disease into two groups: infantile onset (involving the massive enlargement of the heart) and late onset (no heart enlargement): | |
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| Infantile, or early onset, is noticed shortly after [[childbirth|birth]]. Symptoms include severe lack of muscle tone, weakness, and enlarged liver and heart. Mental function is not affected. Development appears normal for the first weeks or months but slowly declines as the disease progresses. Swallowing may become difficult and the [[tongue]] may protrude and become enlarged. Most children die from respiratory or cardiac complications before 2 years of age.
| | ==[[Glycogen storage disease type II overview|Overview]]== |
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| Juvenile onset symptoms appear in early to late childhood and include progressive weakness of respiratory muscles in the trunk, [[diaphragm (anatomy)|diaphragm]] and lower limbs, as well as exercise intolerance. Intelligence is normal.
| | ==[[Glycogen storage disease type II historical perspective|Historical Perspective]]== |
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| Adult onset symptoms also involve generalized muscle weakness and wasting of respiratory muscles in the trunk, lower limbs, and diaphragm. Many patients report respiratory distress, headache at night or upon waking, diminished deep tendon reflexes, and proximal muscle weakness, such as difficulty in climbing stairs. Intellect is not affected. A small number of adult patients live without major symptoms or limitations
| | ==[[Glycogen storage disease type II classification|Classification]]== |
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| ==Treatment== | | ==[[Glycogen storage disease type II pathophysiology |Pathophysiology]]== |
| Cardiac and respiratory complications are treated symptomatically. Physical and occupational therapy may be beneficial for some patients. Alterations in diet may provide temporary improvement but will not alter the course of the disease. Genetic counseling can provide families with information regarding risk in future pregnancies.
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| On April 28, 2006 the US Food and Drug Administration approved a biologics license application (BLA) for [[Myozyme]] (alglucosidase alfa, rhGAA), the first treatment for patients with Pompe disease primarily developed by Dr. Yuan-Tsong Chen (陳垣崇) while he was at [[Duke University]] (Dr. Chen is currently the director of the Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan). Myozyme falls under the FDA Orphan Drug designation and was approved under a priority review. Myozyme is manufactured by Genzyme Corp. in Cambridge, MA, USA. [http://www.fda.gov/bbs/topics/NEWS/2006/NEW01365.html FDA Approval News for Myozyme]
| | ==[[Glycogen storage disease type II causes|Causes]]== |
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| The FDA approved Myozyme for administration by intravenous infusion of solution into a vein. The safety and efficacy of Myozyme were assessed in two separate clinical trials in 39 infantile-onset patients with Pompe disease ranging in age from 1 month to 3.5 years at the time of the first infusion.
| | ==[[Glycogen storage disease type II differential diagnosis|Differentiating Glycogen storage disease type II from other Diseases]]== |
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| Myozyme costs an average of $300,000 a year, and must be taken for the patients' entire life. Some insurers have refused to pay for it.<ref>[http://online.wsj.com/article/SB119007210553130427.html Burden of Proof: As Costs Rise, New Medicines Face Pushback; Insurers Limit Coverage To FDA-Approved Uses; $300,000 Drug Denied] By GEETA ANAND, Wall Street Journal, September 18, 2007</ref>
| | ==[[Glycogen storage disease type II epidemiology and demographics|Epidemiology and Demographics]]== |
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| On August 14, 2006, Health Canada approved Myozyme for the treatment of Pompe disease. On June 14, 2007 the Canadian Common Drug Review issued their recommendations regarding public funding for Myozyme therapy. Their recommendation was to provide funding to treat a very small subset of Pompe patients (Infants less one year of age with Cardiomyopathy).<ref>[http://www.cadth.ca/media/cdr/complete/cdr_complete_Myozyme_June-14-2007_e.pdf] Canadian Common Drug Review Recommendations on Public Funding for Myozyme </ref> The vast majority of developed countries are providing access to therapy for all diagnosed Pompe patients.<ref>[http://www.lexdon.com/article/Genzyme_Reports_Financial_Results_for/45177.html] Genzyme received broad approval in the European Union</ref>
| | ==[[Glycogen storage disease type II risk factors|Risk Factors]]== |
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| ==Prognosis== | | ==[[Glycogen storage disease type II screening|Screening]]== |
| The prognosis for individuals with Pompe disease varies according to the onset and severity of symptoms. Without treatment the disease is particularly lethal in infants and young children.
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| Myozyme (alglucosidase alfa), a recombinant form of the human enzyme acid alpha-glucosidase, is currently being used to replace the missing enzyme. Myozyme helps break down glycogen. In a study<ref>{{cite journal |author=Wagner KR |title=Enzyme replacement for infantile Pompe disease: the first step toward a cure |journal=Neurology |volume=68 |issue=2 |pages=88-9 |year=2007 |pmid=17210887 |doi=10.1212/01.wnl.0000253226.13795.40}}</ref> which included the largest cohort of patients with Pompe disease treated with enzyme replacement therapy (ERT) to date findings showed that Myozyme treatment clearly prolongs ventilator-free survival and overall survival in patients with infantile-onset Pompe disease as compared to an untreated historical control population. Furthermore, the study demonstrated that initiation of ERT prior to 6 months of age, which could be facilitated by newborn screening, shows great promise to reduce the mortality and disability associated with this devastating disorder.
| | ==[[Glycogen storage disease type II natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
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| The only "cure" for Glycogen Storage Disease Type II may ultimately lay in future technologies such as gene therapy.
| | ==Diagnosis== |
| | [[Glycogen storage disease type II diagnostic study of choice|Diagnostic study of Choice]] | [[Glycogen storage disease type II history and symptoms|History and Symptoms]] | [[Glycogen storage disease type II physical examination|Physical Examination]] | [[Glycogen storage disease type II laboratory findings|Laboratory Findings]] | [[Glycogen storage disease type II electrocardiogram|Electrocardiogram]] | [[Glycogen storage disease type II x ray|X Ray]] | [[Glycogen storage disease type II CT|CT]] | [[Glycogen storage disease type II MRI|MRI]] | [[Glycogen storage disease type II echocardiography or ultrasound|Echocardiography or Ultrasound]] | [[Glycogen storage disease type II other imaging findings|Other Imaging Findings]] | [[Glycogen storage disease type II other diagnostic studies|Other Diagnostic Studies]] |
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| ==References== | | ==Treatment== |
| <references/>
| | [[Glycogen storage disease type II medical therapy|Medical Therapy]] | [[Glycogen storage disease type II surgery|Surgery]] | [[Glycogen storage disease type II primary prevention|Primary Prevention]] | [[Glycogen storage disease type II secondary prevention|Secondary Prevention]] | [[Glycogen storage disease type II cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Glycogen storage disease type II future or investigational therapies|Future or Investigational Therapies]] |
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| ==External links== | | ==Case Studies== |
| *[http://www.unitedpompe.com/ United Pompe Foundation]
| | [[Glycogen storage disease type II case study one|Case #1]] |
| *[http://www.pompe.org.uk/ The website of the Pompe's Group of the Association for Glycogen Storage Disease (UK)]
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| *[http://www.worldpompe.org/ International Pompe Association] - A federation of Pompe disease patient's groups world-wide.
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| *[http://www.pompe.com Genzyme's Pompe Information site]
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| *[http://www.fda.gov/bbs/topics/NEWS/2006/NEW01365.html FDA Approval News for Myozyme]
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| *[http://www.pompecanada.com/ Canadian Association of Pompe]
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| [[Category:Endocrinology]]
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| [[Category:Lysosomal storage diseases]]
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| [[Category:Hepatology]]
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| [[Category:Genetic disorders]]
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| [[Category:Inborn errors of metabolism]]
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| [[fr:Maladie de Pompe]] | | [[fr:Maladie de Pompe]] |
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| [[es:Enfermedad de Pompe]] | | [[es:Enfermedad de Pompe]] |
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