AChRAb and MuSKAb double-seropositive myasthenia gravis: a distinct subtype?

INTRODUCTION

This study investigated the characteristics of double-seropositive myasthenia gravis (DSP-MG) in southern China for disease subtype classification.

METHODS

A case-control study was carried out in which the characteristics of DSP-MG patients (n = 17) were compared to those of muscle-specific tyrosine kinase antibody-positive (MuSK)-MG and acetylcholine receptor antibody-positive (AChR)-MG patients (n = 8 and 27, respectively). We also performed a literature review of DSP-MG patients.

RESULTS

Compared to AChR-MG, DSP-MG had greater bulbar dysfunction (47.1% vs 18.6%, P = 0.04), higher incidence of myasthenia crisis (41.2% vs 14.8%, P = 0.04), more severe Myasthenia Gravis Foundation of America classification at maximum worsening, greater autoantibody abnormalities (70.6% vs 33.3%, P = 0.015), greater need for immunosuppressant treatment (58.8% vs 3.7%, P < 0.001), and worse prognosis with less remission (11.8% vs 55.6%, P = 0.001). There were no differences between DSP-MG and MuSK-MG patients. DSP-MG described in published reports was comparable to MuSK-MG.

DISCUSSION: DSP-MG in southern China may be a subtype of MuSK-MG.