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Myofibrillar myopathy
URL of this page: https://medlineplus.gov/genetics/condition/myofibrillar-myopathy/

Myofibrillar myopathy

Description

Myofibrillar myopathy refers to a group of disorders that are characterized by muscle weakness (myopathy) that worsens over time. Myofibrillar myopathy primarily affects the skeletal muscles, which are the muscles that the body uses for movement. In some cases, the heart (cardiac) muscle is also affected.

The signs and symptoms of myofibrillar myopathy vary widely among affected individuals. People with this disorder typically begin to develop myopathy in mid-adulthood. However, the features of this condition can appear anytime between infancy and late adulthood. Myopathy most often begins in the hands, forearms, feet, and lower legs (distal muscles), but some people first experience weakness in the muscles near the center of the body (proximal muscles). The weakness can spread to other muscles. 

Other signs and symptoms of myofibrillar myopathy can include muscle pain (myalgia) and weakness and loss of sensation in the limbs (peripheral neuropathy). Affected individuals may also have skeletal problems, which can include joint stiffness (contractures) and abnormal side-to-side curvature of the spine (scoliosis). Some people with myofibrillar myopathy develop clouding in the lenses of the eyes (cataracts).

Some people with myofibrillar myopathy develop cardiomyopathy, which is a weakening of the heart muscle. In some cases, cardiomyopathy is the first symptom of the disorder.

In rare cases, the muscles used for speaking, swallowing, or breathing are affected in people with myofibrillar myopathy. When the muscles used for breathing are involved, affected individuals may experience extreme tiredness (fatigue), breathing difficulties, and, in severe cases, respiratory failure. 

Frequency

Although myofibrillar myopathy is considered a rare disorder, the exact number of people who have the condition is unknown.

Causes

Variants (also called mutations) in several genes can cause myofibrillar myopathy. These genes provide instructions for making proteins that play an important role in muscle contraction. Within muscle fibers, structures called sarcomeres generate the force needed for muscles to contract. Structures called Z-discs link neighboring sarcomeres together to form myofibrils, which are the basic units of muscle fibers. The organization of sarcomeres and myofibrils provides the strength and stability that is needed during repeated cycles of muscle contraction and relaxation. Many of the genes that are associated with myofibrillar myopathy provide instructions for making proteins that are involved in the function of Z-discs.

Variants in the DES, MYOT, and LDB3 genes are among the main causes of myofibrillar myopathy. Variants in these genes cause cells to produce proteins that do not function properly. Because these abnormal proteins do not interact with Z discs as they should, the coordinated arrangement of sarcomeres and myofibrils is disrupted. Myofibrils that are not formed correctly break down and form clumps (aggregates) of abnormal proteins within the sarcomere, which leads to the myopathy seen in people with myofibrillar myopathy.

Genetic variants are not found in approximately 30 to 50 percent of individuals with myofibrillar myopathy. In these cases, the cause of the condition is unknown.

Learn more about the genes associated with Myofibrillar myopathy

Additional Information from NCBI Gene:

Inheritance

Myofibrillar myopathy has different inheritance patterns depending on which gene is involved.

The condition is typically inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Some cases of myofibrillar myopathy result from new (de novo) variants in the gene that occur during the formation of reproductive cells (eggs or sperm) in an affected individual's parent or during early embryonic development.

In rare cases, myofibrillar myopathy is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell must have a variant to cause the disorder. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but they typically do not show signs and symptoms of the condition.

Other Names for This Condition

  • Myofibrillar myopathies

Additional Information & Resources

Genetic Testing Information

Genetic and Rare Diseases Information Center

Patient Support and Advocacy Resources

Catalog of Genes and Diseases from OMIM

Scientific Articles on PubMed

References

  • Du H, Chen Y, Zeng L, Wu R, Wu T, Zhu J. Myofibrillar myopathies due to a novel mutation in exon 8 of the LDB3 gene. Int J Rheum Dis. 2024 Feb;27(2):e15036. doi: 10.1111/1756-185X.15036. Citation on PubMed
  • Ferrer I, Olive M. Molecular pathology of myofibrillar myopathies. Expert Rev Mol Med. 2008 Sep 3;10:e25. doi: 10.1017/S1462399408000793. Citation on PubMed
  • Fichna JP, Maruszak A, Zekanowski C. Myofibrillar myopathy in the genomic context. J Appl Genet. 2018 Nov;59(4):431-439. doi: 10.1007/s13353-018-0463-4. Epub 2018 Sep 10. Citation on PubMed
  • Kley RA, Olive M, Schroder R. New aspects of myofibrillar myopathies. Curr Opin Neurol. 2016 Oct;29(5):628-34. doi: 10.1097/WCO.0000000000000357. Citation on PubMed
  • Pagola-Lorz I, Vicente E, Ibanez B, Torne L, Elizalde-Beiras I, Garcia-Solaesa V, Garcia F, Delfrade J, Jerico I. Epidemiological study and genetic characterization of inherited muscle diseases in a northern Spanish region. Orphanet J Rare Dis. 2019 Dec 2;14(1):276. doi: 10.1186/s13023-019-1227-x. Citation on PubMed
  • Schroder R, Schoser B. Myofibrillar myopathies: a clinical and myopathological guide. Brain Pathol. 2009 Jul;19(3):483-92. doi: 10.1111/j.1750-3639.2009.00289.x. Citation on PubMed
  • Selcen D, Bromberg MB, Chin SS, Engel AG. Reducing bodies and myofibrillar myopathy features in FHL1 muscular dystrophy. Neurology. 2011 Nov 29;77(22):1951-9. doi: 10.1212/WNL.0b013e31823a0ebe. Epub 2011 Nov 16. Citation on PubMed
  • Selcen D, Ohno K, Engel AG. Myofibrillar myopathy: clinical, morphological and genetic studies in 63 patients. Brain. 2004 Feb;127(Pt 2):439-51. doi: 10.1093/brain/awh052. Epub 2004 Jan 7. Citation on PubMed
  • Selcen D. Myofibrillar myopathies. Curr Opin Neurol. 2010 Oct;23(5):477-81. doi: 10.1097/WCO.0b013e32833d38b0. Citation on PubMed
  • van Spaendonck-Zwarts KY, van Hessem L, Jongbloed JD, de Walle HE, Capetanaki Y, van der Kooi AJ, van Langen IM, van den Berg MP, van Tintelen JP. Desmin-related myopathy. Clin Genet. 2011 Oct;80(4):354-66. doi: 10.1111/j.1399-0004.2010.01512.x. Epub 2010 Jul 21. Citation on PubMed

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