Science News: Epidemiology, Survival, and Clinical Characteristics of Inclusion Body Myositis

Submitted by: Raymond Rosales, MD, PhD
Edited by: Eman Tawfik, MD

Lindgren U, Pullerits R, Lindberg C, Oldfors A. Epidemiology, Survival, and Clinical Characteristics of Inclusion Body Myositis. Ann Neurol. 2022;92(2):201-212. doi:10.1002/ana.26412

Summary: In this study, the authors conducted a population-based study on inclusion body myositis (IBM) with the primary aims to define the disease prevalence, survival rate, and incidence, and to investigate the symptom profiles associated with disease duration and sex over a 33-year period. A total of 128 patients fulfilled the clinicopathological definition of IBM. The disease prevalence was 32 per million inhabitants, 19 per million women, and 45 per million men. The mean incidence was 2.5 per million inhabitants and year. Mean age at symptom onset was 64.4 years with quadriceps weakness being the most common presenting symptom followed by finger flexor weakness. Dysphagia was a common presenting symptom being more frequent in women (23%) than men (10%). The results also revealed decreased survival rate (mean survival was 14 years from symptom onset), and marked sex differences in both prevalence and clinical manifestations.

Autoantibodies to cytosolic 50-nucleotidase 1A were found in 40% of IBM patients and 3.6% of the controls.  A total of 22% had one or more malignancies, compared to the risk of malignancy before 75 years of age in the Western Region, Sweden, during the years 2012 to 2016 of 30.6% for men and 28.3% for women.

Comments: Due to the protractive course and lack of response to immunosuppressive treatment, IBM has a major impact on the activity of daily living in a substantial group of elderly individuals. This emphasizes the importance of knowledge of the diagnosis and typical symptoms and signs to decrease the frequent marked delay in disease diagnosis. Increased awareness of treatable common complications, such as swallowing problems and respiratory dysfunction, as well as sex differences, is important and may improve the impaired survival rate.