2026 American Academy of Neurology Abstract Website

Objective:

To compare clinical and muscle biopsy immunohistochemical findings in inclusion body myositis (IBM) patients based on NT5C1A antibody status.

Background:

IBM is a progressive neuromuscular disease with no cure. NT5C1A antibodies are found in 33–65% of patients, but their relationship to muscle biopsy features remains unclear. Exploring immunohistochemistry in relation to antibody status may reveal IBM subtypes relevant for future research.

Design/Methods:

We retrospectively reviewed clinical and pathological data from IBM patients with known NT5C1A antibody status and available immunohistochemistry at the University of Kansas Medical Center (January 2024–September 2025). Muscle biopsies were re-examined by a blinded neuromuscular reviewer for diagnostic features and staining patterns. Findings were compared between NT5C1A-positive and -negative groups.

Results:

Eight patients were included (mean age 66.4 years, 62.5% male); six were NT5C1A-positive (two weakly positive). No differences were found in clinical features, CK levels, electrodiagnostic data, or H&E histology between groups. All NT5C1A-positive patients showed abnormal p62 staining; one had normal MHC II. Among NT5C1A-negative patients, one (50%) had normal p62 and MHC II. CD3 and CD8 staining was strong in NT5C1A-negative patients but only weak to moderate in NT5C1A-positive ones. CD68 staining was moderate in seronegative and weak in seropositive patients. No other significant immunochemistry staining differences were observed.

Conclusions:

This study is limited by small sample size. Our preliminary findings suggest that NT5C1A-negative IBM patients showed stronger CD3, CD8, and CD68 staining. NT5C1A antibody positivity was not associated with increased histopathological inflammation or more severe immunohistochemical abnormalities.