# The clinical, serological and myopathological features of a cohort of Chinese patients with inclusion body myositis: a single center analysis

## TL;DR

This study analyzed clinical and pathological features of Chinese inclusion body myositis patients, finding earlier onset age and sex-specific differences.

## Contribution

The study reports a high frequency of complement deposition in Chinese IBM patients and its association with disease severity.

## Key findings

- Chinese IBM patients had an earlier age at onset compared to previous reports.
- Complement deposition was observed in 77.4% of patients and linked to more severe muscle weakness.
- Female patients showed higher rates of dysphagia and neck flexor weakness compared to males.

## Abstract

This study aimed to investigate the clinical, serological and myopathological features of Chinese patients with inclusion body myositis (IBM).

This study retrospectively recruited patients diagnosed with IBM according to the 2024 European Neuromuscular Center (ENMC) criteria at Peking University First Hospital between 2004 and 2024. Clinical features, pathological changes and laboratory data were collected. Subgroups were analyzed by sex, dysphagia, anti-cN1A antibody status, and complement deposition.

Forty-three IBM patients (25 males) were included in this cohort. The mean age at onset was 54.9 ± 9.6 years old. All the patients developed weakness in hip flexion, and 81.4% of them with weakness in both knee extension and finger flexion. Dysphagia was reported in 17 patients (39.5%). Endomysial inflammation was observed in all the patients, and 79.1% with rimmed vacuoles, and 76.9% with mitochondrial abnormalities. Female patients more frequently developed dysphagia (P = 0.005) and neck flexion weakness (P < 0.001). Anti-cN1A antibody was positive in 20 patients (66.7%). Seropositive cases were associated with a later age of onset (P = 0.034). Complement deposition was observed in 77.4% of patients and was associated with more severe muscle weakness.

This cohort of Chinese IBM patients suggested an earlier age at onset than previously reported. Hip flexors were most commonly affected. Female patients showed a higher frequency of dysphagia and neck flexor weakness. Our study reported a high frequency of complement deposition in muscle tissue. Complement deposition was associated with disease severity, suggesting a potential role of complement in the pathophysiology of IBM.