Inclusion-Body Myositis (IBM)

Signs and Symptoms

Inclusion body myositis (IBM) usually begins with the gradual onset of slowly progressive weakness in skeletal muscles (muscles that connect to bones and allow movement). Initially, people with IBM may experience some proximal (close to the body center) leg weakness, which can cause difficulty getting up from a chair or frequent falls. Some people may have trouble gripping with their hands, for instance when opening a jar. It is common for people to assume that these initial symptoms are a result of aging. 

IBM symptoms can vary greatly in different people. Most people with IBM experience weakness in the distal (far from the body center) flexor muscles of the wrists and fingers, and the muscles of the front of the thigh (e.g., hip flexors, knee extensors). Asymmetric (on one side of the body) and distal muscle weakness are more likely to appear in IBM than in other IIMs. About half of people with IBM experience difficulty swallowing (dysphagia).

As IBM progresses, most people require assistance with daily activities and some eventually require use of a wheelchair. The timing of these changes is highly variable.

References

1. Greenberg SA. Inclusion body myositis: clinical features and pathogenesis. Nat Rev Rheumatol. 2019;15(5):257-272. doi:10.1038/s41584-019-0186-x
2. Naddaf E. Inclusion body myositis: Update on the diagnostic and therapeutic landscape. Front Neurol. 2022;13:2236. doi:10.3389/FNEUR.2022.1020113/BIBTEX

Last update: Feb 2023
Reviewed by Julie Paik, MD, MHS; Johns Hopkins University