Limb-girdle muscular dystrophy
What is limb-girdle muscular dystrophy?
Limb-girdle muscular dystrophy (LGMD) is not just one genetic disease, it is the name for a group of disorders which have different causes, but many of the same health problems. The common feature of LGMDs is weak and wasted shoulder and hip muscles (the limb-girdles). This weakness usually worsens over time and can cause problems walking, lifting arms, and getting up from sitting. With some forms of LGMD, these muscles can weaken to the point that a wheelchair or other assistive devices are necessary for mobility. Some types of LGMD can also involve the heart (cardiac) and ability to breathe (respiratory muscles).
Different types of LGMD may get worse or progress faster or slower, so identifying the specific cause through genetic testing may be helpful to get an idea of what to expect. Some types progress quickly, causing serious problems moving over the course of a few years, while others may progress very slowly and cause minimal problems.
Voluntary muscles are the muscles that we control to move our bodies. We also have involuntary muscles that we don't consciously control such as the muscles in our digestive system and blood vessels. LGMDs generally don't affect these involuntary muscles, with the exception of the heart which can be affected in some types.
The onset of LGMD can occur during childhood, teenage years, or adulthood. The health problems and severity of the condition can vary from person to person. For example, some individuals with LGMD have very mild symptoms that do not affect lifespan. However, others have severe symptoms that cause them to pass away early. In general, it seems that the later the symptoms appear, the less severe they are.
Intelligence is normal in people affected with LGMDs, as are the senses. Both genders are affected equally.
There are more than 20 types of LGMD, caused by mutations in many different genes. Some are inherited through the family in a dominant manner, while others are inherited in a recessive manner. Limb-girdle muscular dystrophies are separate from the more common X-linked muscle conditions like Duchenne Muscular Dystrophy and Becker Muscular Dystrophy.
More information on the LGMDs can be found at MDA LGMD page
There is a very good summary about LGMD written for healthcare professionals at GeneReviews page for LGMD.
To find a medical professional nearby who can discuss information and testing, A listing of medical geneticists can be found at the American College of Medical Geneticists website and genetic counselors can be found on the National Society of Genetic Counselors website.
- Babameto-Laku, A., Tabaku, M., Tashko, V., Cikuli, M., Mokini, V. The first case of primary alpha-sarcoglycanopathy identified in Albania, in two siblings with homozygous alpha-sarcoglycan mutation. Genet. Counsel. 22: 377-383, 2011. [PubMed: 22303798]
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Are there other names for limb-girdle muscular dystrophy?
Some additional names for limb-girdle muscular dystrophies are listed below:
- Adhalinopathy, primary
- Bethlem myopathy
- Desmin myopathy
- Duchenne-like autosomal recessive muscular dystrophy type 2 (DMDA2)
- Myofibrillar myopathy
- ZASP-related myopathy
What is the usual abbreviation for limb-girdle muscular dystrophy?
Limb-girdle muscular dystrophy is abbreviated LGMD. Autosomal dominant types of LGMD are termed as type 1, therefore the abbreviation becomes LGMD1. Autosomal recessive limb-girdle muscular dystrophies are termed as type 2, therefore the abbreviation for these becomes LGMD2. A letter at the end specifies the specific subtype of limb-girdle muscular dystrophy. For example: limb-girdle muscular dystrophy type 2E can be abbreviated LGMD2E.
- Dominant LGMD subtype abbreviations:
- LGMD1E, also called desmin myopathy
- Recessive LGMD subtype abbreviations:
- LGMD2C, also called SCARMD1
- LGMD2D, also called SCARMD2
Is limb-girdle muscular dystrophy a genetic condition?
Limb-girdle muscular dystrophy (LGMD) refers to a group of genetic conditions. This means that it is caused by a mutation (change) in a gene. A gene is an instruction to our bodies on how to function and develop. Each subtype of LGMD is caused by a change is a different gene. When there is a mutation in a gene, it cannot do its job as well. This causes someone to have the condition.
Limb-girdle muscular dystrophies are divided into two categories depending on how they are inherited.
LGMD type 1 shows dominant inheritance. This means that one faulty copy of a gene, inherited from one parent, is enough to cause the condition.
LGMD type 2 show recessive inheritance. This means that two faulty copies of a gene must be inherited in order to develop the condition, one copy from each parent.
There are many specific subtypes within type 1 and type 2 LGMD.
What does the term “limb girdles” mean?
The term “limb-girdle” is a term that describes voluntary muscles, mainly those close to the body around the hips and shoulders. The shoulder girdle includes the bones and the muscles in the shoulder and upper arms. The pelvic girdle includes the bones and muscles of the pelvic area and thighs. Together these are called the limb girdles. The muscles belonging to the limb girdles are those that are most affected in limb-girdle muscular dystrophies. Voluntary muscles are in the limb girdles are the muscles we control to move our arms and legs.
Is limb-girdle muscular dystrophy more common in any ethnic groups?
There are variations in the prevalence of LGMDs in different populations around the world. However, the exact carrier frequencies are not known. For example: both limb-girdle muscular dystrophy type 2D and limb-girdle muscular dystrophy type 2E can be seen worldwide but are most common in Europe, the United States, and Brazil. LGMD2L makes up about 25% of the type 2 LGMD in the UK.
Is limb-girdle muscular dystrophy more common in males or females?
Dominant and recessive limb-girdle muscular dystrophies affect both males and females equally.
How rare is limb-girdle muscular dystrophy?
Several studies throughout the world have estimated the frequency of LGMDs. Different populations often have different frequencies of the various LGMDs. The overall frequency of all LGMDs has been estimated to be 5-70 people per 1 million in several countries. This is approximately 1 in 14,286 to 1 in 200,000. Some have estimated a slightly smaller prevalence range from 1 in 14,500 to 1 in 123,000 people. LGMD2B is thought to account for 3-19% of all LGMDs. In many studies LGMD2A is the most common (accounting for 8-26% of all LGMDs).
- Masashi Aoki. Dysferlinopathy. GeneReviews. http://www.ncbi.nlm.nih.gov/books/NBK1303/.
- Elena Pegoraro and Eric P Hoffman. Limb-Girdle Muscular Dystrophy Overview. GeneReviews. http://www.ncbi.nlm.nih.gov/books/NBK1408/.
- Glenn Lopate. Limb-Girdle Muscular Dystrophy. Medscape Reference. http://emedicine.medscape.com/article/1170911-overview.