A case of inclusion body myositis responsive to prednisolone therapy

A rare case of sporadic inclusion body myositis and rheumatoid arthritis exhibiting ectopic lymphoid follicle-like structures: a case report and literature review

Sporadic inclusion body myositis (sIBM) is a degenerative, intractable, inflammatory myopathy with an immune pathomechanism. We report on a case of a 44-year-old Japanese man who began developing progressive muscle weakness at age 40. Rheumatoid arthritis symptoms manifested at 43 with strongly positive anti-cyclic citrullinated peptide antibodies. Along with typical sIBM pathology, a muscle biopsy revealed dramatic inflammation with prominent perivascular B-cell infiltration forming ectopic lymphoid follicle-like structures (ELFLSs). Exome sequencing identified no causative variants of hereditary myopathy or immune disorders. A combination of immunotherapy slowed the progression of the muscular symptoms. This unusual form of sIBM, including earlier age at onset, a partial response to immunotherapy, and a histopathology presenting B-cell infiltrate with ectopic lymphoid follicle-like structures, indicates a possible association of rheumatoid arthritis and heterogeneity with the autoimmune involvement of sIBM. We review the clinical and pathological features of patients with rheumatoid arthritis associated sIBM in the literature.

Inclusion body myositis: therapeutic approaches

The idiopathic inflammatory myopathies are a heterogeneous group of diseases that include dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM) and other less common myopathies. These are clinically and histopathologically distinct diseases with many shared clinical features. IBM, the most commonly acquired inflammatory muscle disease occurs in individuals aged over 50 years, and is characterized by slowly progressive muscle weakness and atrophy affecting proximal and distal muscle groups, often asymmetrically. Unlike DM and PM, IBM is typically refractory to immunotherapy. Although corticosteroids have not been tested in randomized controlled trials, the general consensus is that they are not efficacious. There is some suggestion that intravenous immunoglobulin slows disease progression, but its long-term effectiveness is unclear. The evidence for other immunosuppressive therapies has been derived mainly from case reports and open studies and the results are discouraging. Only a few clinical trials have been conducted on IBM, making it difficult to provide clear recommendations for treatment. Moreover, IBM is a slowly progressive disease so assessment of treatment efficacy is problematic due to the longer-duration trials needed to determine treatment effects. Newer therapies may be promising, but further investigation to document efficacy would be expensive given the aforementioned need for longer trials. In this review, various treatments that have been employed in IBM will be discussed even though none of the interventions has sufficient evidence to support its routine use.