What causes inclusion-body myositis (IBM)?
In most cases, the cause of IBM is unclear. For some reason, the body’s immune system turns against its own muscles and damages muscle tissue in an autoimmune process.
Viruses might be a trigger for autoimmune myositis. People with the HIV virus, which causes AIDS, can develop a myositis, as can people with a virus called HTLV-1. Some myositis cases have followed infection with the Coxsackie B virus.