Longitudinal dynamics and clinical significance of acetylcholine receptor blocking antibodies in myasthenia gravis.

OBJECTIVES

To investigate the longitudinal clinical relevance of acetylcholine receptor (AChR) blocking antibodies in myasthenia gravis (MG).

METHODS

We prospectively studied 47 AChR-positive MG patients with 121 serial antibody measurements over a mean follow-up of 2.8 years. AChR-binding antibodies were measured by a conventional radioimmunoprecipitation assay, whereas AChR-blocking activity was measured using a competitive radioimmunoassay. Disease severity was assessed using Myasthenia Gravis Foundation of America (MGFA) classification. Longitudinal associations were analyzed using generalized estimating equations (GEE).

RESULTS

Blocking antibodies (> 20% inhibition) were associated with MGFA severity across repeated observations in longitudinal GEE analysis (β = 0.045, p < 0.001), whereas binding antibodies were not significant. Among 13 patients with ocular-onset MG, all 8 who progressed to generalized disease were blocking antibody-positive, while none of the 5 patients who remained ocular tested positive. Blocking antibodies were detected in 90.5% of generalized MG patients, whereas all persistently ocular patients were negative.

CONCLUSIONS

AChR blocking antibodies are associated with MG disease severity over time and may help identify ocular MG patients at risk of generalization, supporting their potential clinical relevance in MG.