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Original Contribution
August 2007

Classification of Myasthenia Gravis Based on Autoantibody Status

Author Affiliations

Author Affiliations: Department of Neurology (Drs S. Suzuki and N. Suzuki) and Division of Rheumatology, Department of Internal Medicine (Drs Satoh and Kuwana), Keio University School of Medicine, Tokyo; and Departments of Neurology, Hanamaki General Hospital, Hanamaki (Drs Utsugisawa and Nagane), and Iwate Medical University, Morioka (Dr Terayama), Japan.

Arch Neurol. 2007;64(8):1121-1124. doi:10.1001/archneur.64.8.1121

Objectives  To investigate the autoantibody status of patients with myasthenia gravis (MG) and to evaluate its usefulness for disease classification.

Design  Retrospective cohort study of patients with MG, who have autoantibodies to receptors and ion channels expressed at neuromuscular junctions and in muscles that impair neuromuscular transmission. One of the autoantibodies studied was a recently identified, novel, MG-specific autoantibody to a voltage-gated potassium (Kv) channel, Kv1.4.

Setting  Keio University Hospital, Tokyo, and Iwate Medical University Hospital, Morioka.

Patients  Two hundred nine patients with MG.

Main Outcome Measures  Anti-Kv1.4 antibody was measured by an immunoprecipitation assay with sulfur 35–labeled extract from rhabdomyosarcoma cells. Antititin antibody was detected with a commercially available enzyme-linked immunosorbent assay.

Results  Anti–acetylcholine receptor, anti-Kv1.4, and antititin antibodies were detected in 150 (72%), 26 (12%), and 50 (24%) of the 209 patients with MG, respectively. All of the patients who were positive for anti-Kv1.4 or antititin antibody were seropositive for the anti–acetylcholine receptor antibody. They were classified into 4 groups based on their status in regard to 3 MG-related autoantibodies: anti-Kv1.4, antititin, and anti–acetylcholine receptor. Clinical associations were found between anti-Kv1.4 and bulbar involvement, myasthenic crisis, thymoma, and concomitant myocarditis and/or myositis; between antititin and older-onset MG; between anti–acetylcholine receptor alone and younger-onset MG; and between seronegativity and ocular MG. In addition, patients with MG in the anti-Kv1.4 group had more severe manifestations of disease than those in the other 3 groups.

Conclusion  Classification of patients with MG based on autoantibody status may be useful in defining clinical subsets.