[The etiology and pathogenesis of sporadic inclusion body myositis]

Area of Science:

• Neurology
• Pathology
• Genetics

Context:

• Sporadic inclusion body myositis (sIBM) is the most prevalent acquired muscle disease affecting the elderly.
• Clinical manifestations include progressive muscle weakness and atrophy, particularly in the quadriceps, wrist, and finger flexors.
• The underlying etiology and pathogenesis of sIBM are not fully elucidated, with potential contributions from genetic, aging, and environmental factors.

Purpose:

• To summarize the current understanding of sporadic inclusion body myositis (sIBM), focusing on its clinical features, pathological characteristics, and etiological considerations.
• To highlight the ongoing debate regarding the classification of sIBM as either an inflammatory myositis or a myodegenerative disorder.
• To underscore the therapeutic challenges associated with sIBM, noting its general refractoriness to immune therapies.

Summary:

• sIBM presents with characteristic muscle weakness and atrophy, primarily affecting limb muscles in older individuals.
• Pathologically, sIBM exhibits unique features of inflammation within muscle fibers and the presence of cytoplasmic and intranuclear inclusions containing Alzheimer-type proteins.
• The differential diagnosis involves considering sIBM as either a T cell-mediated inflammatory myopathy or a degenerative condition marked by protein aggregation and secondary inflammation.

Impact:

• Provides a concise overview of sIBM for researchers, clinicians, and patients.
• Highlights key areas of uncertainty in sIBM pathogenesis, guiding future research directions.
• Emphasizes the need for novel therapeutic strategies given the limited efficacy of current immune-based treatments for sIBM.