Spinal muscular atrophy

Información en español Title

Summary Summary

Spinal muscular atrophy (SMA) refers to a group of inherited conditions that affect the muscles. The severity of the condition; the associated signs and symptoms; and the age at which symptoms develop varies by subtype. In general, people with SMA experience progressive weakness and atrophy of muscles involved in mobility, the ability to sit unassisted, and head control. Breathing and swallowing may also be affected in severe cases.^[1]^[2]^[3] SMA is generally caused by changes (mutations) in the SMN1 gene and is inherited in an autosomal recessive manner. Extra copies of the SMN2 gene modify the severity of SMA. Rare autosomal dominant (caused by mutations in DYNC1H1 or VAPB) and X-linked (caused by mutations in UBA1) forms of SMA exist.^[4] Treatment is based on the signs and symptoms present in each person.^[5]^[2]

Last updated: 1/7/2016

Symptoms Symptoms

Spinal muscular atrophy (SMA) is primarily characterized by progressive muscle weakness and atrophy. Depending on the type, onset may range from before birth to adolescence or young adulthood.^[6]

SMA type 0 (the prenatal form) is the most severe form and begins before birth. Usually, the first symptom of type 0 is reduced movement of the fetus that is first seen between 30 and 36 weeks of the pregnancy. After birth, these newborns have little movement and have difficulties with swallowing and breathing.^[1] Life span is approximately 2-6 months.^[6]

There are 3 types of SMA that tend to affect children before the age of one (SMA type I, SMA type II, and X-linked SMA). SMA type 1 is a severe form that may be apparent at birth or the first few months of life. Features may include difficulty swallowing or breathing and inability to sit without support.^[4] The life span is usually less than 2 years.^[6] SMA type II typically becomes apparent between 6 and 12 months of age; affected children may sit without support, although they cannot stand or walk unaided.^[4] About 70% of people with this type live to be at least 25 years of age.^[6] X-linked infantile SMA is similar to SMA type I; additional features may include joint deformities (contractures) or even broken bones at birth in very severe cases.^[4]

Three other types of SMA can affect people in early childhood and adulthood.^[4] SMA type III (also called Kugelberg-Welander disease or juvenile type) is a milder form of spinal muscular atrophy with symptoms that generally appear between early childhood (older than age 1 year) and early adulthood. People with type III are able to stand and walk without help, although they usually lose this ability later in life.^[1] SMA type IV and Finkel type occur in adulthood, usually after age 30. Symptoms of adult-onset SMA are usually mild to moderate and include muscle weakness, tremor and twitching.^[1]

Last updated: 1/7/2016

Inheritance Inheritance

Most forms of spinal muscular atrophy (types I, II, III, and IV, specifically) are inherited in an autosomal recessive pattern.^[4] This means that to be affected, a person must have a mutation in both copies of the responsible gene in each cell. The parents of an affected person usually each carry one mutated copy of the gene and are referred to as carriers. Carriers typically do not show signs or symptoms of the condition. When two carriers of an autosomal recessive condition have children, each child has a 25% (1 in 4) risk to have the condition, a 50% (1 in 2) risk to be a carrier like each of the parents, and a 25% chance to not have the condition and not be a carrier.

Finkel type spinal muscular atrophy is inherited in an autosomal dominant pattern, which means an affected person only needs a mutation in one copy of the responsible gene in each cell.^[4]

X-linked infantile spinal muscular atrophy is inherited in an X-linked pattern. The gene associated with this condition is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder. Because it is unlikely that females will have two altered copies of this gene, males are affected by X-linked disorders much more frequently than females. A striking characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.^[4]

Last updated: 1/7/2016

Treatment Treatment

Unfortunately, there is currently no cure for spinal muscular atrophy. Treatment is supportive and based on the signs and symptoms present in each person.^[1]

The Spinal Muscular Atrophy Foundation offers many patient resources regarding the treatment and management of people with spinal muscular atrophy. To access these resources, please click on the link.

CureSMA has a Web page entitled "Living with SMA" which includes management options for some of the key medical issues associated with spinal muscular atrophy and strategies for daily care.

Last updated: 1/8/2016

Management Guidelines

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.

Prognosis Prognosis

The long-term outlook (prognosis) for people with spinal muscular atrophy varies by subtype. Even within a subtype, lifespan can vary based on the severity of the case, the associated symptoms and the response to treatment (i.e. respiratory therapy, nutrition support, and physical therapy).^[7]

In general, the lifespan in spinal muscular atrophy type 1 is often less than two years due to respiratory problems and infections. Although survival time with type II is often longer, many affected people pass away during childhood. Children with type III disease may survive into adulthood. Affected people who do not develop symptoms of SMA until adulthood generally have a normal life expectancy.^[2]^[7]

Last updated: 1/8/2016

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Research Research

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

ClinicalTrials.gov lists trials that are studying or have studied Spinal muscular atrophy. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.
The Research Portfolio Online Reporting Tool (RePORT) provides access to reports, data, and analyses of research activities at the National Institutes of Health (NIH), including information on NIH expenditures and the results of NIH-supported research. Although these projects may not conduct studies on humans, you may want to contact the investigators to learn more. To search for studies, enter the disease name in the "Text Search" box. Then click "Submit Query".

Organizations Organizations

Nonprofit support and advocacy groups bring together patients, families, medical professionals, and researchers. These groups often raise awareness, provide support, and develop patient-centered information. Many are the driving force behind research for better treatments and possible cures. They can direct people to research, resources, and services. Many groups also have experts who serve as medical advisors. Visit their 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

Cure SMA
925 Busse Road
Elk Grove, IL 60007
Toll-free: 800-886-1762
Telephone: 847-367-7620
Fax: 847-367-7623
E-mail: info@curesma.org
Website: http://www.curesma.org
Muscular Dystrophy Association (MDA)
222 S Riverside Plaza
Suite 1500
Chicago, IL 60606
Toll-free: 800-572-1717
TTY: 1-800-572-1717
E-mail: mda@mdausa.org
Website: http://www.mdausa.org/
Spinal Muscular Atrophy Foundation
888 Seventh Avenue
Suite 400
New York, NY 10019
Toll-free: 877-FUND-SMA (877-386-3762)
Telephone: 646-253-7100
Fax: 212-247-3079
E-mail: info@smafoundation.org
Website: http://www.smafoundation.org

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Learn More 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

Families of SMA has created a booklet entitled Understanding SMA that is intended to serve as a source of information and support for children and adults with Spinal Muscular Atrophy (SMA).
Genetics Home Reference (GHR) contains information on Spinal muscular atrophy. This website is maintained by the National Library of Medicine.
MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
The National Human Genome Research Institute's (NHGRI) website has an information page on this topic. NHGRI is part of the National Institutes of Health and supports research on the structure and function of the human genome and its role in health and disease.
The National Institute of Neurological Disorders and Stroke (NINDS) collects and disseminates research information related to neurological disorders. Click on the link to view information on this topic.
The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
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.
PubMed is a searchable database of medical literature and lists journal articles that discuss Spinal muscular atrophy. Click on the link to view a sample search on this topic.

News & Events News & Events

News

GARD Information Navigator
May 10, 2016

NCATS Co-Sponsored Conferences

18th Annual International Spinal Muscular Atrophy Research Group Meeting Thursday, June 12, 2014 - Saturday, June 14, 2014
Location: Gaylord National , National Harbor, MD
Description:
The overall goal of the meeting is to provide a venue for researchers to share unpublished data and to develop collaborations, with the intent of accelerating the discovery of a treatment for this devastating disease. In addition, the specific aims for the conference are: 1.To enable open communication of early, unpublished scientific data, accelerating the pace of research. 2.To provide a forum to discuss timely topics in SMA openly with the entire research community. 3. To create a sense of community among SMA researchers, resulting in productive research partnerships.

Contact: Dr. John D. Porter(301) 496-5739 porterjo@ninds.nih.gov

Co-funding Institute(s): National Institute of Neurological Disorders and Stroke, Office of Rare Diseases Research
Third Genome Dynamics in the Neurosciences Conference Sunday, July 18, 2010 - Thursday, July 22, 2010
Location: The Hilton Metropole, Brighton, England
Description: The goal of this meeting was to integrate basic processes of DNA damage signaling and repair and clinical aspects of neurological and neurodegenerative disease. The program was designed to bring together leading scientists with primary interests in DNA damage signaling with those working in specific related neurodegenerative disease areas as a means for integrating these fields. It was anticipated that this would generate insights into how normal processes of genome maintenance in the brain contribute to the prevention of a wide range of diseases.

Contact: Dr. Danilo A. Tagle, NINDS(301) 496-5745tagled@mninds.nih.gov

Co-funding Institute(s): National Institute of Neurological Disorders and Stroke, Office of Rare Diseases Research
- Agenda ( - 42KB)
- Speakers ( - 47KB)
- Summary ( - 13KB)
14th International Spinal Muscular Atrophy Research Group Meeting Thursday, June 24, 2010 - Sunday, June 27, 2010
Location: Santa Clara, California
Description: The overall meeting goal was to bring together junior and established spinal muscular atrophy (SMA) research experts from around the world to share unpublished data and foster a spirit of communication and collaboration. The majority of the leading investigators in SMA attend this conference each year. The conference also brought in young and new researchers into the SMA community, including those located internationally, who do not have opportunities to interact with the recognized thought leaders in this area. It arguably represents the best networking opportunity in the SMA field.

Contact: Dr. John D. Porter(301) 496-5739 porterjo@ninds.nih.gov

Co-funding Institute(s): National Institute of Neurological Disorders and Stroke, Office of Rare Diseases Research
- Agenda ( - 22KB)

Related Diseases Related Diseases

The following diseases are related to Spinal muscular atrophy. If you have a question about any of these diseases, you can contact GARD.

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Are there any other diseases or conditions that have similar symptoms to SMA, or mimic the symptoms of SMA? See answer
My brother's daughter was recently diagnosed with spinal muscular atrophy. What can you you tell me about this condition, particularly as it relates to the SMN genes? Can this condition be treated? What is the prognosis? See answer

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References References

Learning About Spinal Muscular Atrophy. National Human Genome Research Institute. 2012; http://www.genome.gov/20519681.
Spinal muscular atrophy. MedlinePlus. February 2014; http://www.nlm.nih.gov/medlineplus/ency/article/000996.htm.
Spinal Muscular Atrophy. National Organization for Rare Disorders. 2012; http://www.rarediseases.org/search/rdbdetail_abstract.html?disname=Spinal+Muscular+Atrophy.
Spinal muscular atrophy. Genetics Home Reference (GHR). January 2013; http://ghr.nlm.nih.gov/condition/spinal-muscular-atrophy.
Bryan Tsao, MD. Spinal Muscular Atrophy. Medscape Reference. December 2015; http://emedicine.medscape.com/article/1181436-overview.
Thomas W Prior, PhD, FACMG and Barry S Russman, MD. Spinal Muscular Atrophy. GeneReviews. November 2013; http://www.ncbi.nlm.nih.gov/books/NBK1352/.
About SMA: Frequently Asked Questions. SMA Foundation. http://www.smafoundation.org/about-sma/faq/. Accessed 1/8/2016.