Inclusion body myositis: evolving concepts

Abstract

Purpose of review: To discuss recent developments in our understanding of epidemiology, diagnostics, biomarkers, pathology, pathogenesis, outcome measures, and therapeutics in inclusion body myositis (IBM).

Recent findings: Recent epidemiology data confirms a relatively higher prevalence in the population aged above 50 years and the reduced life expectancy. Association with cancer and other systemic disorders is better defined. The role of magnetic resonance imaging (MRI) and ultrasound in diagnosis as well as in following disease progression has been elucidated. There are new blood and imaging biomarkers that show tremendous promise for diagnosis and as outcome measures in therapeutic trials. Improved understanding of the pathogenesis of the disease will lead to better therapeutic interventions, but also highlights the importance to have sensitive and responsive outcome measures that accurately quantitate change.

Summary: There are exciting new developments in our understanding of IBM which should lead to improved management and therapeutic options.

Figure 1:

A conceptual framework for disease overlap and spectrum in polymyositis/Inclusion Body Myositis. In some patients disease phenotype morphs, and is associated with a progressive increase in 1) percentage of immunosenescent highly differentiated (apoptosis-resistant) T lymphocytes, 2) mitochondrial deletions and myopathological features of mitochondrial dysfunction, 3) rimmed vacuoles, and 4) accumulation of a vast array of proteins, including p62, TDP-43, etc. Inflammatory infiltrates generally reduce over time as the above changes occur.