Glycogen storage disease type V: Difference between revisions
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==Pathophysiology== | ==Pathophysiology== | ||
* Glycogen storage disease type VI is caused by the deficiency of liver Myophosphorylase. | |||
* Normal function of phophorylase is :- <ref name="pmid25914343">{{cite journal |vauthors=Nogales-Gadea G, Brull A, Santalla A, Andreu AL, Arenas J, Martín MA, Lucia A, de Luna N, Pinós T |title=McArdle Disease: Update of Reported Mutations and Polymorphisms in the PYGM Gene |journal=Hum. Mutat. |volume=36 |issue=7 |pages=669–78 |year=2015 |pmid=25914343 |doi=10.1002/humu.22806 |url=}}</ref> | |||
** Phosphorylase maintains the glucose homeostasis. | |||
** It leads to the degradation of glycogen into glucose-1-phosphate. | |||
** Alpha-1,4-glucoside residues are removed from the outer branches of the glycogen molecule. | |||
** Degradation is done until glycogen is broken down to branches of approximately 4 glucosyl units. | |||
* 3 isozymes are found in the muscles,liver and brain. | |||
* Myophosphorylase is the isozyme specific to muscles. | |||
* Carbohydrate metabolic pathways are blocked which lead to accumulation of excess glycogen. | |||
* Muscles are unable to produce energy from glycogen due to deficiency of this enzyme. | |||
* There occurs increase in the Cellular mechanical stress due to :- | |||
** Accumulation of glycogen stores. | |||
** Downregulation of sodium-potassium pumps. | |||
** Elevation of sarcoplasmic calcium. | |||
* All this can lead to rhabdomyolysis.<ref name="pmid25053163">{{cite journal |vauthors=Nogales-Gadea G, Santalla A, Brull A, de Luna N, Lucia A, Pinós T |title=The pathogenomics of McArdle disease--genes, enzymes, models, and therapeutic implications |journal=J. Inherit. Metab. Dis. |volume=38 |issue=2 |pages=221–30 |year=2015 |pmid=25053163 |doi=10.1007/s10545-014-9743-2 |url=}}</ref> | |||
* Muscle damage is done due to oxidative stress and purine nucleotide metabolism. | |||
* Hypoglycemia is not seen as liver phosphorylase is not involved. | |||
=== Genetics === | |||
* Myophosphorylase deficiency is an autosomal recessive disorder. | |||
* Mutations occurs in the muscle isoform of phosphorylase - PYGM. | |||
* ''PYGM is'' located at chromosome 11q13. <ref name="pmid259143432">{{cite journal |vauthors=Nogales-Gadea G, Brull A, Santalla A, Andreu AL, Arenas J, Martín MA, Lucia A, de Luna N, Pinós T |title=McArdle Disease: Update of Reported Mutations and Polymorphisms in the PYGM Gene |journal=Hum. Mutat. |volume=36 |issue=7 |pages=669–78 |year=2015 |pmid=25914343 |doi=10.1002/humu.22806 |url=}}</ref> | |||
* Affected individual carries one normal allele and one pathogenic allele. | |||
* Each pregnancy | |||
** 25% chance of the baby developing myophosphorylase deficiency by inheriting two alleles containing a pathogenic mutation. | |||
** 50% are unaffected carriers - one normal allele and one pathogenic allele. | |||
*** Carriers of myophosphorylase deficiency do not become symptomatic. | |||
** 25% are normal - inheriting two normal copies of the gene. | |||
* Disease severity can be correlated with the genotype at the angiotensin-converting enzyme (ACE) locus. | |||
==Causes== | ==Causes== | ||
* The most common cause of glycogen storage disease type V is the deficiency of muscle myophosphorylase, a muscle isoform of the enzyme glycogen phosphorylase. | |||
* It occurs due to a mutation in the gene PYGM located at chromosome 11q13. | |||
==Differentiating {{PAGENAME}} from Other Diseases== | ==Differentiating {{PAGENAME}} from Other Diseases== | ||
Line 41: | Line 73: | ||
* The prevalence of McArdle's disease is approximately 1 in 100,000 individuals in Texas, USA.<ref name="pmid10891971">{{cite journal |vauthors=Haller RG |title=Treatment of McArdle disease |journal=Arch. Neurol. |volume=57 |issue=7 |pages=923–4 |year=2000 |pmid=10891971 |doi= |url=}}</ref> | * The prevalence of McArdle's disease is approximately 1 in 100,000 individuals in Texas, USA.<ref name="pmid10891971">{{cite journal |vauthors=Haller RG |title=Treatment of McArdle disease |journal=Arch. Neurol. |volume=57 |issue=7 |pages=923–4 |year=2000 |pmid=10891971 |doi= |url=}}</ref> | ||
* McArdle's disease commonly affects individuals in the 2nd-3rd decade of life. | |||
==Risk Factors== | ==Risk Factors== | ||
* The most potent risk factor in the development of glycogen storage disease type VI is a family member with glycogen storage disease type V. | |||
==Screening== | ==Screening== | ||
Line 50: | Line 84: | ||
==Diagnosis== | ==Diagnosis== | ||
===Diagnostic Criteria=== | ===Diagnostic Criteria=== | ||
There are no established criteria for the [[diagnosis]] of glycogen storage disease type V. | |||
===History and Symptoms=== | ===History and Symptoms=== |
Revision as of 21:49, 24 January 2018
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Glycogen storage disease type V | |
ICD-10 | E74.0 |
---|---|
ICD-9 | 271.0 |
OMIM | 232600 |
DiseasesDB | 5307 |
eMedicine | med/911 |
MeSH | D006012 |
Overview
Glycogen storage disease type V is a metabolic disorder, more specifically a glycogen storage disease, caused by a deficiency of myophosphorylase.
GSD type V is also known as McArdle's disease or muscle phosphorylase deficiency. The disease was first reported in 1951 by Dr. Brian McArdle of Guy's Hospital, London.[1]
People with this disease experience difficulty when their muscles are called upon to perform relatively brief yet intense activity. The inability to break down glycogen into glucose results in an energy shortage within the muscle, resulting in muscle pain and cramping, and sometimes causing serious injury to the muscles. The typical features of McArdle disease include exercise intolerance with myalgia, early fatigue, and stiffness of exercising muscles, which are sometimes relieved by rest. Following a short period of rest, most patients experience a second wind and can resume exercise with less difficulty.The prevailing levels of fatty acids as potential energy sources for muscle may account for the second wind phenomenon. In addition, rhabdomyolysis—the breakdown of muscle tissue—can cause myoglobinuria, a red-to-brown-colored urine. The myoglobinuria can cause kidney damage. The disease is hereditary and is inherited as an autosomal recessive trait. Anaerobic exercise must be avoided but regular gentle aerobic exercise is beneficial.
Historical Perspective
- McArdle's disease was first described by Brian McArdle, a Scottish physician, in 1951.[2]
- In 1993, the first PYGM pathogenic mutations were described.[3]
Classification
Pathophysiology
- Glycogen storage disease type VI is caused by the deficiency of liver Myophosphorylase.
- Normal function of phophorylase is :- [4]
- Phosphorylase maintains the glucose homeostasis.
- It leads to the degradation of glycogen into glucose-1-phosphate.
- Alpha-1,4-glucoside residues are removed from the outer branches of the glycogen molecule.
- Degradation is done until glycogen is broken down to branches of approximately 4 glucosyl units.
- 3 isozymes are found in the muscles,liver and brain.
- Myophosphorylase is the isozyme specific to muscles.
- Carbohydrate metabolic pathways are blocked which lead to accumulation of excess glycogen.
- Muscles are unable to produce energy from glycogen due to deficiency of this enzyme.
- There occurs increase in the Cellular mechanical stress due to :-
- Accumulation of glycogen stores.
- Downregulation of sodium-potassium pumps.
- Elevation of sarcoplasmic calcium.
- All this can lead to rhabdomyolysis.[5]
- Muscle damage is done due to oxidative stress and purine nucleotide metabolism.
- Hypoglycemia is not seen as liver phosphorylase is not involved.
Genetics
- Myophosphorylase deficiency is an autosomal recessive disorder.
- Mutations occurs in the muscle isoform of phosphorylase - PYGM.
- PYGM is located at chromosome 11q13. [6]
- Affected individual carries one normal allele and one pathogenic allele.
- Each pregnancy
- 25% chance of the baby developing myophosphorylase deficiency by inheriting two alleles containing a pathogenic mutation.
- 50% are unaffected carriers - one normal allele and one pathogenic allele.
- Carriers of myophosphorylase deficiency do not become symptomatic.
- 25% are normal - inheriting two normal copies of the gene.
- Disease severity can be correlated with the genotype at the angiotensin-converting enzyme (ACE) locus.
Causes
- The most common cause of glycogen storage disease type V is the deficiency of muscle myophosphorylase, a muscle isoform of the enzyme glycogen phosphorylase.
- It occurs due to a mutation in the gene PYGM located at chromosome 11q13.
Differentiating Glycogen storage disease type V from Other Diseases
Epidemiology and Demographics
- The prevalence of McArdle's disease is approximately 1 in 167,000 individuals in spanish community.[7]
- The prevalence of McArdle's disease is approximately 1 in 100,000 individuals in Texas, USA.[8]
- McArdle's disease commonly affects individuals in the 2nd-3rd decade of life.
Risk Factors
- The most potent risk factor in the development of glycogen storage disease type VI is a family member with glycogen storage disease type V.
Screening
Natural History, Complications, and Prognosis
Diagnosis
Diagnostic Criteria
There are no established criteria for the diagnosis of glycogen storage disease type V.
History and Symptoms
Physical Examination
Laboratory Findings
Imaging Findings
Other Diagnostic Studies
- McArdles disease is genetically heterogeneous.
- Most common mutation that is seen in McArdle's disease is substitution of thymine for cytosine at codon 49.
- In 90% patients, their leukocyte can be used to make diagnosis.
- By doing this muscle biopsy can be avoided.
Treatment
Medical Therapy
Surgery
Prevention
External links
References
- ↑ Template:WhoNamedIt
- ↑ McARDLE B (1951). "Myopathy due to a defect in muscle glycogen breakdown". Clin Sci. 10 (1): 13–35. PMID 24540673.
- ↑ Bartram C, Edwards RH, Clague J, Beynon RJ (1993). "McArdle's disease: a nonsense mutation in exon 1 of the muscle glycogen phosphorylase gene explains some but not all cases". Hum. Mol. Genet. 2 (8): 1291–3. PMID 8401511.
- ↑ Nogales-Gadea G, Brull A, Santalla A, Andreu AL, Arenas J, Martín MA, Lucia A, de Luna N, Pinós T (2015). "McArdle Disease: Update of Reported Mutations and Polymorphisms in the PYGM Gene". Hum. Mutat. 36 (7): 669–78. doi:10.1002/humu.22806. PMID 25914343.
- ↑ Nogales-Gadea G, Santalla A, Brull A, de Luna N, Lucia A, Pinós T (2015). "The pathogenomics of McArdle disease--genes, enzymes, models, and therapeutic implications". J. Inherit. Metab. Dis. 38 (2): 221–30. doi:10.1007/s10545-014-9743-2. PMID 25053163.
- ↑ Nogales-Gadea G, Brull A, Santalla A, Andreu AL, Arenas J, Martín MA, Lucia A, de Luna N, Pinós T (2015). "McArdle Disease: Update of Reported Mutations and Polymorphisms in the PYGM Gene". Hum. Mutat. 36 (7): 669–78. doi:10.1002/humu.22806. PMID 25914343.
- ↑ Lucia A, Ruiz JR, Santalla A, Nogales-Gadea G, Rubio JC, García-Consuegra I, Cabello A, Pérez M, Teijeira S, Vieitez I, Navarro C, Arenas J, Martin MA, Andreu AL (2012). "Genotypic and phenotypic features of McArdle disease: insights from the Spanish national registry". J. Neurol. Neurosurg. Psychiatry. 83 (3): 322–8. doi:10.1136/jnnp-2011-301593. PMID 22250184.
- ↑ Haller RG (2000). "Treatment of McArdle disease". Arch. Neurol. 57 (7): 923–4. PMID 10891971.
Template:Endocrine, nutritional and metabolic pathology