Autoantibodies in thymoma-associated myasthenia gravis with myositis or neuromyotonia.
BACKGROUND
About 50% of patients with thymoma have paraneoplastic myasthenia gravis (MG). Myositis and myocarditis or neuromyotonia (NMT) will also develop in some. Patients with thymoma-associated MG produce autoantibodies to a variety of neuromuscular antigens, particularly acetylcholine receptor (AChR), titin, skeletal muscle calcium release channel (ryanodine receptor [RyR]), and voltage-gated potassium channels (VGKC).


OBJECTIVE
To examine whether neuromuscular autoantibodies in patients with thymoma correlate with specific clinical syndromes.


METHODS
Serum and plasma samples from 19 patients with thymoma-associated MG, of whom 5 had myositis and 6 had NMT, underwent testing for antibodies to AChR, titin, RyR, and VGKC.


RESULTS
Antibodies to AChR and titin were found in 19 and 17 patients, respectively. Antibodies to RyR correlated with the presence of myositis (P = .03); they were found in all 5 patients with myositis and in only 1 patient with NMT, but also in 4 of 8 patients with neither disease. Antibodies to VGKC were found in 4 patients with NMT, 1 of 3 patients undergoing testing for myositis, and 2 of 7 patients undergoing testing with neither comorbidity. Presence of RyR antibodies correlated with high levels of titin antibodies.


CONCLUSIONS
The results appear to distinguish partially between 3 groups of patients with thymoma-associated MG: the first with RyR antibodies and myositis or myocarditis, the second with NMT without RyR antibodies, and the third without RyR antibodies, myositis, or NMT. Differences in the thymoma may underlie these pathologic associations.
Mygland
A
A
Department of Neurology, University of Bergen, Norway. aase.mygland@c2i.net
Vincent
A
A
Newsom-Davis
J
J
Kaminski
H
H
Zorzato
F
F
Agius
M
M
Gilhus
N E
NE
Aarli
J A
JA
D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D002276:Carcinoid Tumor / Q000453:epidemiology / Q000276:immunology* / Q000473:pathology; D015897:Comorbidity; D064211:Connectin; D004576:Electromyography; D005260:Female; D006801:Humans; D020386:Isaacs Syndrome / Q000175:diagnosis / Q000453:epidemiology / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009124:Muscle Proteins / Q000276:immunology; D009157:Myasthenia Gravis / Q000453:epidemiology / Q000276:immunology*; D009205:Myocarditis / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology / Q000276:immunology; D009220:Myositis / Q000175:diagnosis / Q000453:epidemiology / Q000276:immunology*; D010257:Paraneoplastic Syndromes / Q000175:diagnosis / Q000453:epidemiology / Q000276:immunology; D015221:Potassium Channels / Q000276:immunology; D011237:Predictive Value of Tests; D011494:Protein Kinases / Q000276:immunology; D011950:Receptors, Cholinergic / Q000276:immunology; D019837:Ryanodine Receptor Calcium Release Channel / Q000276:immunology; D013945:Thymoma / Q000453:epidemiology / Q000276:immunology* / Q000473:pathology; D013953:Thymus Neoplasms / Q000453:epidemiology / Q000276:immunology* / Q000473:pathology
D001323:Autoantibodies; D064211:Connectin; D009124:Muscle Proteins; D015221:Potassium Channels; D011950:Receptors, Cholinergic; D019837:Ryanodine Receptor Calcium Release Channel; C577285:TTN protein, human; D011494:Protein Kinases