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Laing distal myopathy
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Reviewed August 2008
What is Laing distal myopathy?
Laing distal myopathy is a condition that affects skeletal muscles, which are muscles that the body uses for movement. This disorder causes progressive muscle weakness that appears in childhood. The first sign of Laing distal myopathy is usually weakness in certain muscles in the feet and ankles. This weakness leads to tightening of the Achilles tendon (the band that connects the heel of the foot to the calf muscles), an inability to lift the first (big) toe, and a high-stepping walk. Months to years later, muscle weakness develops in the hands and wrists. Weakness in these muscles makes it difficult to lift the fingers, particularly the third and fourth fingers. Many affected people also experience hand tremors.
In addition to muscle weakness in the hands and feet, Laing distal myopathy causes weakness in several muscles of the neck and face. A decade or more after the onset of symptoms, mild weakness also spreads to muscles in the legs, hips, and shoulders. Laing distal myopathy progresses very gradually, and most affected people remain mobile throughout life. Life expectancy is normal in people with this condition.
How common is Laing distal myopathy?
Although Laing distal myopathy is thought to be rare, its prevalence is unknown. Several families with the condition have been identified worldwide.
What genes are related to Laing distal myopathy?
Mutations in the MYH7 gene cause Laing distal myopathy. The MYH7 gene provides instructions for making a protein that is found in heart (cardiac) muscle and in type I skeletal muscle fibers. Type I fibers, which are also known as slow-twitch fibers, are one of two types of fibers that make up skeletal muscles. Type I fibers are the primary component of skeletal muscles that are resistant to fatigue. For example, muscles involved in posture, such as the neck muscles that hold the head steady, are made predominantly of type I fibers.
In cardiac and skeletal muscle cells, the protein produced from the MYH7 gene forms part of a larger protein called type II myosin. This type of myosin generates the mechanical force that is needed for muscles to contract. In the heart, regular contractions of cardiac muscle pump blood to the rest of the body. The coordinated contraction and relaxation of skeletal muscles allow the body to move.
It is unknown how mutations in the MYH7 gene cause progressive muscle weakness in people with Laing distal myopathy. Researchers have proposed that these mutations alter the structure of myosin in skeletal muscles, which prevents it from interacting with other proteins. The abnormal myosin gradually impairs the function of type I skeletal muscle fibers.
In most people with Laing distal myopathy, the signs and symptoms of the disorder are limited to weakness of skeletal muscles. Although myosin made with the MYH7 protein is also found in cardiac muscle, it is unclear why heart problems are not a typical feature of this condition.
Read more about the MYH7 gene.
How do people inherit Laing distal 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 most cases, an affected person inherits the mutation from one affected parent. A small percentage of cases result from new mutations in the gene. These cases occur in people with no history of the disorder in their family.
Where can I find information about diagnosis or management of Laing distal myopathy?
These resources address the diagnosis or management of Laing distal myopathy and may include treatment providers.
General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about Laing distal myopathy?
You may find the following resources about Laing distal myopathy helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What other names do people use for Laing distal myopathy?
What if I still have specific questions about Laing distal myopathy?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding Laing distal myopathy?
Achilles tendon ; autosomal ; autosomal dominant ; cardiac ; cell ; contraction ; distal ; gene ; muscular dystrophy ; mutation ; myosin ; prevalence ; protein ; sign ; skeletal muscle ; tendon ; type I skeletal muscle fibers
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (5 links)
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? in the Handbook.