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Patients with myasthenia gravis who are triply seronegative for antibodies appear to have a milder course of the disease, but frequently have ocular manifestations of the autoimmune disease, researchers said at the American Association’s annual meeting. of Neuromuscular & Electrodiagnostic Medicine.

Jonathan Morena, DO, resident in neurology at Wexner Medical Center at Ohio State University in Columbus, retrospectively reviewed the charts of 255 patients with myasthenia gravis, including 21 with triple negative pathology.

“The triply seronegative patients required significantly fewer immunosuppressive agents than patients who tested positive for acetylcholine receptor antibodies (p= 0.0001), and they tended to have a history of less frequent hospitalizations, myasthenic seizures and intubations compared to all antibody positive groups, ”Dr. Morena said in his presentation.

Researchers reviewed Ohio State University records from 2009 to 2019. Triple seronegative myasthenia gravis was defined by history and examination consistent with myasthenia gravis and positive single-fiber electromyography, repetitive nerve stimulation, or edrophonium test, but negative for acetylcholine receptor antibodies, anti-muscle-specific tyrosine kinase and lipoprotein-related protein 4 antibodies.

They identified 210 patients who were positive for acetylcholine receptor antibodies, nine patients who were positive for muscle-specific tyrosine kinase; six patients who had lipoprotein-bound protein 4 antibodies; nine patients had double seronegative myasthenia gravis and 21 patients were triple seronegative patients.,

Dr Moreno and colleagues found that 33% of patients with triple seronegative myasthenia gravis had eye disease, which was significantly higher than 13% of those who tested positive for acetylcholine receptor antibodies (p =0.0250). One patient with triple myasthenia gravis and one double seronegative patient presented with thymic hyperplasia and improvement after thymectomy. Eleven patients with triple seronegative myasthenia gravis had negative genetic tests for congenital myasthenic syndrome.

“Although probably rare, screening for thymic pathology should be considered even in seronegative myasthenia gravis, and thymectomy should be considered when there are thymic abnormalities on imaging,” said Dr Morena. “We have not found any other diagnoses in patients with seronegative myasthenia gravis. Thus, ancillary testing should be considered in patients carefully selected for cost-effective care.”

Commenting on the study, Robert Lisak, MD, FAAN, Parker Webber Chair in Neurology, Professor of Neurology, and Professor of Biochemistry, Microbiology and Immunology at Wayne State University in Detroit, explained, “In myasthenia gravis, antibodies block, alter, or destroy acetylcholine receptors at the neuromuscular junction, preventing the muscle from contracting. This is most often caused by antibodies to the acetylcholine receptor itself, but antibodies to other proteins, such as muscle-specific protein kinase, can also impair transmission at the neuromuscular junction.

“The results of a recent multicenter study that found that a small percentage of those who are doubly seronegative have antibodies to lipoprotein-bound protein 4 and do not appear to differ from patients who are positive for acetylcholine receptor antibodies, although they are not yet fully determined, are useful, Dr. Lisak said Neurology today At the Meetings.The current study suggests that the triple negative patients have mild and often eye disease, although about 50 percent of the eyepieces are positive for acetylcholine receptor antibodies, so there is an overlap. ”

“We should realize that the triple negatives might have different antibodies among them, yet to be discovered,” he said.

“So far,” he said, “the differences in response to some therapies are most notable between patients who are positive for acetylcholine receptor antibodies and patients who are positive for muscle-specific tyrosine kinase. Therapies aimed at inhibiting complement activation should not work in myasthenia gravis specific to muscle tyrosine kinase since the antibodies are IgG4 and do not bind or activate complement.

“Muscle-specific tyrosine kinase patients often do not respond to acetylcholine esterase inhibitors and sometimes get worse. IVIg appears to be more effective in patients with anti-acetylcholine receptor antibodies than in muscle-specific tyrosine kinase positive myasthenia gravis patients, and rituximab is more effective in patients with muscle-specific tyrosine kinase. “

Dr Morena did not disclose any relationship with the industry.
Dr Lisak has revealed his relationships with Argenx, Guidepoint, Clearview, Clarivate and Guidepointe.

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AANEM Abstract 1: Morena J, Jiang B, Freimer M, et al. Characteristics of triple seronegative myasthenia gravis. An experience in one center.

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