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


METHODS
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.


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


METHODS
Two hundred nine patients with MG.


METHODS
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.


CONCLUSIONS
Classification of patients with MG based on autoantibody status may be useful in defining clinical subsets.
Suzuki
Shigeaki
S
Department of Neurology, Keio University School of Medicine, 35 Shinanomachi, Tokyo 160-8582, Japan. shigeaki@sc.itc.keio.ac.jp
Utsugisawa
Kimiaki
K
Nagane
Yuriko
Y
Satoh
Takashi
T
Terayama
Yasuo
Y
Suzuki
Norihiro
N
Kuwana
Masataka
M
D000328:Adult; D000367:Age Factors; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D015331:Cohort Studies; D064211:Connectin; D005260:Female; D006801:Humans; D047468:Immunoprecipitation; D051665:Kv1.4 Potassium Channel / Q000276:immunology; D008297:Male; D008875:Middle Aged; D009124:Muscle Proteins / Q000276:immunology; D009157:Myasthenia Gravis / Q000145:classification* / Q000150:complications / Q000276:immunology* / Q000503:physiopathology; D009205:Myocarditis / Q000150:complications; D009220:Myositis / Q000150:complications; D011494:Protein Kinases / Q000276:immunology; D011950:Receptors, Cholinergic / Q000276:immunology; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013945:Thymoma / Q000150:complications; D013953:Thymus Neoplasms / Q000150:complications
D001323:Autoantibodies; D064211:Connectin; D051665:Kv1.4 Potassium Channel; D009124:Muscle Proteins; D011950:Receptors, Cholinergic; C577285:TTN protein, human; D011494:Protein Kinases