Myopathy, Myofibrillar

Myopathy, Myofibrillar

National Organization for Rare Disorders, Inc.

Important

It is possible that the main title of the report Myopathy, Myofibrillar is not the name you expected.

Disorder Subdivisions

  • desminopathy
  • alpha-B crystallinopathy
  • myotilinopathy
  • filaminopathy
  • BAG3-related myofibrillar myopathy
  • zaspopathy

General Discussion

Myofibrillar myopathies are a group of rare genetic neuromuscular disorders that may be diagnosed in childhood but most often appear after 40 years of age. These conditions are highly variable but are characterized by a slowly progressive muscle weakness that can involve skeletal and smooth muscle. Skeletal muscle weakness can be present in the muscles close to the center of the body (proximal) as well as the distal muscles. A weakening of the heart muscle (cardiomyopathy) is common and may manifest as arrhythmia, conduction defects or congestive heart failure.

Symptoms

Most affected individuals with mofibrillar myopathy secondary to desmin mutations present with a slowly progressive muscle weakness. Distal muscle weakness is more common than proximal weakness but variable presentation within the same family occurs. Some also have muscle stiffness, aching, cramps or decreased muscle mass (atrophy). Pain, loss of sensation and inability to control muscles may also occur in one form (Filamin C protein mutations). Cardiomyopathy is sometimes the presenting symptom and may manifest as arrhythmia, conduction defects or congestive heart failure.



Children with desminopthies may present with cardiomyopathy. Children with BAG3-related myofibrillar myopathies may present in the first or second decade with proximal weakness, respiratory failure and restrictive cardiomyopathy and are frequently rapidly progressive and fatal.

Causes

Myofibrillar myopathies are usually inherited as adult autosomal dominant genetic conditions though children with recessive presentation of Desmin mutation do occur and in this case presentation can be in early childhood. It is not always possible to determine the mode of inheritance in families because some mildly affected individuals remain undiagnosed and others are diagnosed late in life.



Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary to cause a particular disease. The abnormal gene can be inherited from either parent or can be the result of a new mutation (gene change) in the affected individual. Approximately 25% of affected individuals have an affected parent. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy. The risk is the same for males and females.



The genes responsible for myofibrillar myopathies have been identified in approximately 20% of affected individuals. These disorders have been categorized by the gene involved. The gene abnormality results in excess amounts of a particular protein in muscle.



Desminopathy---(onset 20-30) DES gene/desmin protein

Alpha-B crystallinopathy---(onset 20-40 years)CRYAB gene/a-B crystallin protein

Myotilinopathy---(Onset 27-77) Titin immunoglobulin domain protein TTID gene/myotilin protein

Filaminopathy---(onset 37-57) FLNC gene/filamin C protein

BAG3-related myofibrillar myopathy---(onset childhood) BCL2-associated athanogene 3/ BaG3 protein

Zaspopathy---(onset 44-73 years)LDB3 (ZASP) gene/LIM domain-binding protein 3

Affected Populations

The frequency of myofibrillar myopathies has not been estimated. It is likely that these conditions are unrecognized and underdiagnosed.

Standard Therapies

Diagnosis

A diagnosis of myofibrillar myopathies is made based on clinical findings, electromyography, nerve conduction studies and muscle biopsy. Molecular genetic testing for the DES, CRYAB, MYOT, LDB3 and ZASP genes is available to confirm the diagnosis. Molecular genetic testing for the BAG3 gene is available on a research basis only.



Treatment

Individuals affected with cardiomyopathy may consider implantation of a mechanical device to regulate heartbeat (pacemaker) and cardioverter defibrillator (ICD). Heart transplantation may be considered if the cardiomyopathy is progressive or life threatening. Respiratory therapy and physical therapy may be helpful for those with advanced muscle weakness. Orthotics may be helpful if foot drop develops.

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.



For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:



Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov



For information about clinical trials sponsored by private sources, contact:

www.centerwatch.com

References

TEXTBOOKS

Connolly AM. Myofibrillar (Desmin and Desmin-Related) Myopathy. In: The NORD Guide to Rare Disorders, Philadelphia: Lippincott, Williams and Wilkins, 2003:630-631.



JOURNAL ARTICLES

Selcen D, Muntoni F, Burton BK, et al. Mutation in BAG3 causes severe dominant childhood muscular dystrophy. Ann Neurol. 2009; 65: 83



Fischer D, Clemen CS, Olive M, et al. Different early pathogenesis in myotilinopathy compared to primary desminopathy. Neuromuscul Disord. 2006; 16: 361-7.



Penisson-Besnier I, Talvinen K, Dumez C, et al. Myotilinopathy in a family with late onset myopathy. Neuromuscul Disord. 2006; 16: 427-31.



Selcen D, Engel AG. Mutations in ZASP define a novel form of muscular dystrophy in humans. Ann Neurol. 2005; 57: 269-76.



Selcen D, Ohno K, Engel AG. Myofibrillar myopathy: clinical, morphological and genetic studies in 63 patients. Brain. 2004; 127: 439-51.



Goldfarb LG, Vicart P, Goebel HH, et al.. Desmin myopathy. Brain. 2004; 127: 723-34.



Selcen D, Engel AG. Mutations in myotilin cause myofibrillar myopathy. Neurology. 2004; 62: 1363-71.



Selcen D, Engel AG. Myofibrillar myopathy caused by novel dominant negative alpha B-crystallin mutations. Ann Neurol. 2003; 54: 804-10.



Sugawara M, et al. A novel de novo mutation in the desmin gene causes desmin myopathy with toxic aggregates. Neurology. 2000;55:986-90.



Dalakas MC, et al. Desmin myopathy, a skeletal myopathy with cardiomyopathy caused by mutations in the desmin gene. New Engl J Med. 2000;342:770-80.



Li D, et al. Desmin mutation responsible for idiopathic dilated cardiomyopathy. Circulation. 1999;100:461-64.



Fidzianska A, et al. Familial inclusion body myopathy with desmin storage. Acta Neuropathol (Berl). 1999;97:509-14.



Goldfarb LG, et al. Missense mutations in desmin associated with familial cardiac and skeletal myopathy. Nature Genet. 1998;19:402-03.



Horowitz SH, et al. Autosomal dominant distal myopathy with desmin storage: a clinicopathologic and electrophysiologic study of a large kinship. Muscle Nerve. 1994;17:151-60.



Vajsar j, et al. Familial desminopathy: myopathy with accumulation of desmin-type intermediate filaments. J Neurol Neurosurg Psychiatry. 1993;56:644-48.



FROM THE INTERNET

Selcen, D and Engel, AG, (Updated 2/2/10). Myofibrillar Myopathy. In: GeneReviews at GeneTests: Medical Genetics Information Resource (database online). Copyright, University of Washington, Seattle. 1997-2010, Available at http://www.genetests.org. Accessed 3/10.



Haberler C, Gelpi E and Budka H. Myofibrillar Myopathies; Orphanet: http://www.orpha.net/data/patho/GB/uk-MyofibrillarMyopathies.pdf, Last Update: 3/05, Accessed 3/10.

Resources

Sudden Arrhythmia Death Syndromes Foundation

508 E. South Temple

Suite 202

Salt Lake City, UT 84102

USA

Tel: (801)531-0937

Fax: (801)531-0945

Tel: (800)786-7723

Email: laura@sads.org

Internet: http://www.sads.org



Muscular Dystrophy Association

3300 East Sunrise Drive

Tucson, AZ 85718-3208

USA

Tel: (520)529-2000

Fax: (520)529-5300

Tel: (800)572-1717

Email: mda@mdausa.org

Internet: http://www.mda.org/



Muscular Dystrophy Campaign

61 Southwark Street

London, SE1 0HL

United Kingdom

Tel: 02078034800

Email: info@muscular-dystrophy.org

Internet: http://www.muscular-dystrophy.org



Cardiac Arrhythmias Research and Education Foundation, Inc. (C.A.R.E)

427 Fulton Street

P.O. Box 69

Seymour, WI 54165

USA

Fax: (920)833-7005

Tel: (800)404-9500

Email: care@careforhearts.org

Internet: http://www.longqt.org or http://www.careforhearts.org



For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc.® (NORD). Cigna members can access the complete report by logging into myCigna.com. For non-Cigna members, a copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html.

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