Inclusion Body Myositis (IBM) is a chronic progressive muscular disease observed primarily in people aged 50 years or more. Weakness and atrophy are seen in the quadriceps and in the finger/wrist flexors. The inability to stand–up, cane–dependent gait, inability to open a plastic bottle, choking on food ingestion, and being wheelchair–bound appear to be the typical IBM milestones. Dysphagia may result in aspiration pneumonia. Falls and fractures associated with knee breaks are frequently seen.
Rimmed vacuoles and infiltration of mononuclear cells in non–necrotic fibers can be found in the muscle tissue of IBM patients. IBM is generally refractory to current therapy, such as steroids and immunosuppressant agents. Although IBM is rarely observed in Japan compared with Europe and the United States, it has been observed more frequently over the past 30 years in Japan. In a society where the number of elderly people increases, the number of individuals with IBM would also increase. This review provides an overview of the clinical features, pathobiological mechanisms, biomarkers, and therapeutic strategies for IBM.