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Inclusion-Body Myositis (IBM)

Signs and Symptoms

Inclusion-body myositis (IBM) primarily affects men, although women can be affected. It occurs mainly in those older than age 50.1

IBM usually begins with the gradual onset of slowly progressive weakness in skeletal muscles. Initially, patients experience some difficulty getting up after sitting in a chair. Some patients may have trouble gripping, for instance when opening a jar. Rarely, patients may experience difficulty swallowing. The majority of IBM patients experience weakness in the distal finger flexor muscles, as well as weakness and atrophy in the quadriceps (knee extensors).2,3 The following features can be seen as well:

  • Unlike other idiopathic inflammatory myopathies, asymmetric and distal muscle weakness are more likely to appear, with a very slow disease progression.
  • Both proximal leg and distal arm muscle groups are usually involved (proximal muscles are closer to the torso, distal muscles are further away from the torso).2,3
  • Mild muscle pain (myalgias) may appear frequently.4
  • Muscle atrophy is progressive, and strength declines.

IBM is generally a slowly progressing disease, and life expectancy is not significantly affected. Most people with IBM remain able to walk, although they may require a cane or wheelchair for long distances. Some are more profoundly affected and require a wheelchair full-time within 10 or 15 years of their first symptoms.

For stories of families living with IBM, see our stories on Strongly, the MDA blog.


  1. Manuscript, A. Miositis por cuerpos de inclusión. Neurol Clin 29, 997–1003 (2014).
  2. Lloyd, T. E. et al. Evaluation and construction of diagnostic criteria for inclusion body myositis. Neurology (2014). doi:10.1212/WNL.0000000000000642
  3. Cox, F. M. et al. A 12-year follow-up in sporadic inclusion body myositis: An end stage with major disabilities. Brain (2011). doi:10.1093/brain/awr217
  4. Beyenburg, S., Zierz, S. & Jerusalem, F. Inclusion body myositis?: clinical and histopathological features of 36 patients. Clin. Investig. (1993). doi:10.1007/BF00186623

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