title: Acetylcholine receptor antibodies in the Lambert-Eaton myasthenic syndrome.
abstract: Two patients were initially diagnosed with myasthenia gravis with elevated titers of acetylcholine receptor antibodies. Features including weakness that normalized with sustained contraction, areflexia, autonomic symptoms, and low-amplitude baseline compound muscle action potentials with abnormal increments following brief exercise and high-frequency repetitive stimulation, however, suggested that these patients had Lambert-Eaton myasthenic syndrome. One patient had antibodies directed against presynaptic calcium channels, confirming the diagnosis. The second patient was seronegative for these antibodies but had elevated titers of antistriated muscle antibodies. This shows that serologic studies can conflict with clinical and electrodiagnostic findings in patients with Lambert-Eaton syndrome. These cases also point out that acetylcholine receptor antibodies are not necessarily diagnostic of myasthenia gravis in patients with Lambert-Eaton syndrome. Instead, these antibodies could represent a nonpathogenic epiphenomenon.
authors.affiliation: Department of Neurology, University of Texas, Southwestern Medical Center, Dallas 75235-8897, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Katz
authors.forename: G I
authors.initials: GI
authors.lastname: Wolfe
authors.forename: W W
authors.initials: WW
authors.lastname: Bryan
authors.forename: R
authors.initials: R
authors.lastname: Tintner
authors.forename: R J
authors.initials: RJ
authors.lastname: Barohn
mesh_terms: D000200:Action Potentials; D000368:Aged; D001323:Autoantibodies / Q000097:blood*; D015220:Calcium Channels / Q000276:immunology; D003937:Diagnosis, Differential; D004558:Electric Stimulation; D004568:Electrodiagnosis; D005260:Female; D006801:Humans; D015624:Lambert-Eaton Myasthenic Syndrome / Q000175:diagnosis / Q000276:immunology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology; D009157:Myasthenia Gravis / Q000175:diagnosis / Q000276:immunology / Q000503:physiopathology; D005082:Physical Exertion; D011950:Receptors, Cholinergic / Q000276:immunology*; D014459:Ulnar Nerve / Q000503:physiopathology
chemical_list: D001323:Autoantibodies; D015220:Calcium Channels; D011950:Receptors, Cholinergic