Myosin storage myopathy

Reviewed February 2013

What is myosin storage myopathy?

Myosin storage myopathy is a condition that causes muscle weakness (myopathy) that does not worsen or worsens very slowly over time. This condition is characterized by the formation of protein clumps, which contain a protein called myosin, within certain muscle fibers. The signs and symptoms of myosin storage myopathy usually become noticeable in childhood, although they can occur later. Because of muscle weakness, affected individuals may start walking later than usual and have a waddling gait, trouble climbing stairs, and difficulty lifting the arms above shoulder level. Muscle weakness also causes some affected individuals to have trouble breathing.

How common is myosin storage myopathy?

Myosin storage myopathy is a rare condition. Its prevalence is unknown.

What genes are related to myosin storage myopathy?

Mutations in the MYH7 gene cause myosin storage myopathy. The MYH7 gene provides instructions for making a protein known as the cardiac beta (β)-myosin heavy chain. This protein is found in heart (cardiac) muscle and in type I skeletal muscle fibers, one of two types of fibers that make up the muscles that the body uses for movement. Cardiac β-myosin heavy chain is the major component of the thick filament in muscle cell structures called sarcomeres. Sarcomeres, which are made up of thick and thin filaments, are the basic units of muscle contraction. The overlapping thick and thin filaments attach to each other and release, which allows the filaments to move relative to one another so that muscles can contract.

Mutations in the MYH7 gene lead to the production of an altered cardiac β-myosin heavy chain protein, which is thought to be less able to form thick filaments. The altered proteins accumulate in type I skeletal muscle fibers, forming the protein clumps characteristic of the disorder. It is unclear how these changes lead to muscle weakness in people with myosin storage myopathy.

Related Gene(s)

Changes in this gene are associated with myosin storage myopathy.

MYH7

How do people inherit myosin storage myopathy?

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

In some cases, an affected person inherits the mutation from one affected parent. Other cases result from new mutations in the gene and occur in people with no history of the disorder in their family.

Where can I find information about diagnosis or management of myosin storage myopathy?

These resources address the diagnosis or management of myosin storage myopathy and may include treatment providers.

Genetic Testing Registry: Myopathy, myosin storage (http://www.ncbi.nlm.nih.gov/gtr/conditions/C1842160)

You might also find information on the diagnosis or management of myosin storage myopathy in Educational resources (http://www.ghr.nlm.nih.gov/condition/myosin-storage-myopathy/show/Educational+resources) and Patient support (http://www.ghr.nlm.nih.gov/condition/myosin-storage-myopathy/show/Patient+support).

General information about the diagnosis (http://ghr.nlm.nih.gov/handbook/consult/diagnosis) and management (http://ghr.nlm.nih.gov/handbook/consult/treatment) of genetic conditions is available in the Handbook. Read more about genetic testing (http://ghr.nlm.nih.gov/handbook/testing), particularly the difference between clinical tests and research tests (http://ghr.nlm.nih.gov/handbook/testing/researchtesting).

To locate a healthcare provider, see How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

Where can I find additional information about myosin storage myopathy?

You may find the following resources about myosin storage myopathy helpful. These materials are written for the general public.

MedlinePlus - Health information
- Encyclopedia: Muscle Function Loss (http://www.nlm.nih.gov/medlineplus/ency/article/003190.htm)
- Health Topic: Muscle Disorders (http://www.nlm.nih.gov/medlineplus/muscledisorders.html)
Additional NIH Resources - National Institutes of Health
National Institute of Neurological Disorders and Stroke: Congenital Myopathy Information Page (http://www.ninds.nih.gov/disorders/myopathy_congenital/myopathy_congenital.htm)
Educational resources - Information pages
- Muscular Dystrophy Association: Facts About Myopathies (http://static.mda.org/publications/PDFs/FactsAboutMyopathies.pdf)
- Muscular Dystrophy Campaign: Myopathy (http://www.muscular-dystrophy.org/about_muscular_dystrophy/conditions/116_myopathy)
- New York Presbyterian Hospital: Myopathy (http://nyp.org/services/neuroscience/myopathy.html)
Patient support - For patients and families
- Muscular Dystrophy Association (http://mda.org/)
- Muscular Dystrophy Campaign (http://www.muscular-dystrophy.org/)
- We Move (http://www.wemove.org/)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

Genetic Testing Registry - Repository of genetic test information
- Genetic Testing Registry: Myopathy, myosin storage (http://www.ncbi.nlm.nih.gov/gtr/conditions/C1842160)
PubMed - Recent literature (http://www.ncbi.nlm.nih.gov/pubmed?term=((myosin%20storage%20myopathy%5BTIAB%5D)%20OR%20(autosomal%20dominant%20hyaline%20body%20myopathy%5BTIAB%5D))%20AND%20english%5Bla%5D%20AND%20human%5Bmh%5D%20AND%20%22last%203600%20days%22%5Bdp%5D)
OMIM - Genetic disorder catalog (http://omim.org/entry/608358)

What other names do people use for myosin storage myopathy?

autosomal dominant hyaline body myopathy

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines (http://ghr.nlm.nih.gov/ConditionNameGuide) and How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

What if I still have specific questions about myosin storage myopathy?

Ask the Genetic and Rare Diseases Information Center (http://rarediseases.info.nih.gov/GARD/).

What glossary definitions help with understanding myosin storage myopathy?

autosomal ; autosomal dominant ; cardiac ; cell ; contraction ; gait ; gene ; inclusion body ; mutation ; myosin ; myosin heavy chain ; prevalence ; protein ; skeletal muscle ; type I skeletal muscle fibers

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.ghr.nlm.nih.gov/glossary).

References

Armel TZ, Leinwand LA. Mutations in the beta-myosin rod cause myosin storage myopathy via multiple mechanisms. Proc Natl Acad Sci U S A. 2009 Apr 14;106(15):6291-6. doi: 10.1073/pnas.0900107106. Epub 2009 Mar 31. (http://www.ncbi.nlm.nih.gov/pubmed/19336582?dopt=Abstract)
Pegoraro E, Gavassini BF, Borsato C, Melacini P, Vianello A, Stramare R, Cenacchi G, Angelini C. MYH7 gene mutation in myosin storage myopathy and scapulo-peroneal myopathy. Neuromuscul Disord. 2007 Apr;17(4):321-9. Epub 2007 Mar 2. (http://www.ncbi.nlm.nih.gov/pubmed/17336526?dopt=Abstract)
Tajsharghi H, Oldfors A. Myosinopathies: pathology and mechanisms. Acta Neuropathol. 2013 Jan;125(1):3-18. doi: 10.1007/s00401-012-1024-2. Epub 2012 Aug 5. (http://www.ncbi.nlm.nih.gov/pubmed/22918376?dopt=Abstract)
Tajsharghi H, Thornell LE, Lindberg C, Lindvall B, Henriksson KG, Oldfors A. Myosin storage myopathy associated with a heterozygous missense mutation in MYH7. Ann Neurol. 2003 Oct;54(4):494-500. (http://www.ncbi.nlm.nih.gov/pubmed/14520662?dopt=Abstract)

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.



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