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Disease Profile

Limb-girdle muscular dystrophy type 1B

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

Unknown

Age of onset

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ICD-10

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Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

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Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Other names (AKA)

LGMD1B; Muscular dystrophy, proximal, type 1B

Categories

Congenital and Genetic Diseases; Heart Diseases; Nervous System Diseases

Summary

Limb-girdle muscular dystrophy type 1B (LGMD1B) is one of many types of limb-girdle muscular dystrophy. These diseases affect the voluntary muscles, which are the muscles that are moved on purpose, such as the arms, legs, fingers, toes, and facial muscles. Specifically, LGMD1B causes muscle weakness in the lower limbs. The muscle weakness typically affects the muscles closest to the center of the body (proximal muscles) such as the upper legs. The disease is progressive, leading to a loss of muscle strength and bulk over a number of years.[1]

Limb-girdle muscular dystrophy type 1B is caused by mutations (changes) to the LMNA gene. The disease is inherited in an autosomal dominant manner. A diagnosis of LGMD1B is suspected in people who have signs and symptoms consistent with the disease, and the diagnosis can be confirmed with laboratory tests. While there are not treatments that can reverse the muscle weakness associated with the disease, supportive treatment can decrease the complications.[1]

Symptoms

Limb-girdle muscular dystrophy type 1B (LGMD1B) causes muscle weakness, especially in the lower limbs. The muscle weakness typically affects the muscles closest to the center of the body (proximal muscles) such as the upper legs. The muscle weakness can cause an unusual walking gait and difficulty running or using the stairs. The disease is progressive, leading to a loss of muscle strength and bulk over a number of years.[1][2] Later in adulthood, the muscles of the upper body may also become affected.[3]

The symptoms of LGMD1B can begin at any time between childhood and adulthood. About half of all affected individuals show signs of the disease in childhood. Other symptoms of the disease may include difficulty straightening the elbows (elbow contracture) and heart problems including arrhythmia or left ventricular hypertrophy. The signs and symptoms of people with LGMD1B can vary, even among members of the same family.[1] 

Cause

Limb-girdle muscular dystrophy type 1B is caused by mutations (changes) to the LMNA gene. The LMNA gene provides instructions to the body to make a protein that is responsible for providing stability and strength to the cells. Specifically, LMNA provides instructions to make a protein that is located in the nuclear envelope, which surrounds the nucleus. The proteins of the nuclear envelope help move molecules in and out of the nucleus. When there are changes to the LMNA gene, this protein is not made correctly. It is not clear exactly why changes in this gene cause the signs and symptoms associated with LGMD1B, but it is thought that the protein created by the LMNA gene may be important for controlling the expression of other genes.[4]

Diagnosis

Limb-girdle muscular dystrophy type 1B (LGMD1B) is typically suspected when a person has signs or symptoms consistent with the disease. The doctor may wish to take a thorough personal and family history and to run some laboratory tests. These tests may include:[1]

In some cases, genetic testing of genes associated with muscular dystrophies may be ordered to confirm the diagnosis.[1] 

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

    Treatment

    Unfortunately, there is no cure for limb-girdle muscular dystrophy type 1B (LGMD1B). Treatment options that may be recommended for people with LGMD1B may include:[1]

    • Weight control to avoid obesity
    • Physical therapy and stretching exercises to prevent contractures of the elbows
    • Use of mechanical aids such as canes, walkers, and wheelchairs
    • Monitoring for evidence of heart problems

    In some cases, a pacemaker may be necessary to treat heart problems associated with LGMD1B. It is recommended that people with LGMD1B be provided with social and emotional support to cope with the diagnosis. Other specialists that may be recommended include a neurologist, cardiologist, occupational therapist, nutritionist, and genetic counselor.[1] 

    Organizations

    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Supporting this Disease

      Organizations Providing General Support

        Learn more

        These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

        Where to Start

        • Genetics Home Reference (GHR) contains information on Limb-girdle muscular dystrophy type 1B. This website is maintained by the National Library of Medicine.

          In-Depth Information

          • GeneReviews provides current, expert-authored, peer-reviewed, full-text articles describing the application of genetic testing to the diagnosis, management, and genetic counseling of patients with specific inherited conditions.
          • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
          • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
          • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
          • PubMed is a searchable database of medical literature and lists journal articles that discuss Limb-girdle muscular dystrophy type 1B. Click on the link to view a sample search on this topic.

            References

            1. Pegoraro E and Hoffman EP. Limb-Girdle Muscular Dystrophy Overview. GeneReviews. August 30, 2012; https://www.ncbi.nlm.nih.gov/books/NBK1408/.
            2. Limb-girdle muscular dystrophy. Genetics Home Reference (GHR). December 2014; https://ghr.nlm.nih.gov/condition/limb-girdle-muscular-dystrophy.
            3. Muscular Dystrophy; Limb-Girdle, Type 1B; LGMD1B. Online Mendelian Inheritance in Man. March 27, 2017; https://www.omim.org/entry/159001.
            4. LMNA gene. Genetics Home Reference (GHR). June 2017; https://ghr.nlm.nih.gov/gene/LMNA.
            5. Ambrosi P, Mouly-Bandini A, Attarian S, and Habib G. Heart transplantation in 7 patients from a single family with limb-girdle muscular dystrophy caused by lamin A/C mutation. International Journal of Cardiology. November 12, 2009; 137(3):e75-76. https://www.ncbi.nlm.nih.gov/pubmed/19446900.

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