AUTHOR=Nes Magne Solberg , Haugen Mette , Haugland Hans Kristian , Gilhus Nils Erik , Vedeler Christian Alexander 

TITLE=Case report: Seropositive myasthenia gravis complicated by limbic encephalitis positive for antibodies to AMPAR and Lgi1

JOURNAL=Frontiers in Neurology

VOLUME=Volume 14 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2023.1237140

DOI=10.3389/fneur.2023.1237140

ISSN=1664-2295

ABSTRACT=Objectives
Autoantibodies to the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) and leucine-rich glioma-inactivated 1 (Lgi1) are associated with autoimmune encephalitis. We describe an acetylcholine receptor (AChR) positive patient with myasthenia gravis who developed limbic encephalitis with antibodies to AMPAR and Lgi1

Methods
A single case report with detailed, prospective clinical and biomarker data including serial laboratory testing and histopathology.

Results
A 49-year-old female was diagnosed with anti-AChR antibody positive generalized myasthenia gravis in 1983. Nine months after the removal of a thymoma in 1984, she developed influenza-like symptoms and then symptoms of limbic encephalitis. Retrospective analysis of serum showed high concentrations of anti-AMPAR and lower concentrations of anti-Lgi1 antibodies. Cerebral CT was normal, EEG showed bifrontal dysrhythmia and CSF mild pleocytosis. Immuno-histochemical examination of the thymoma confirmed staining for Glur2, a subunit of AMPAR. The patient recovered with mild sequelae, but low levels of anti-AMPAR and anti-Lgi1 antibodies were detectable for over 25 years subsequently. 

Discussion
This case confirms earlier reports of AMPAR-associated autoimmune encephalitis co-occurring with thymoma and myasthenia gravis and is unique in its observational length. It shows, moreover, that antibodies to AMPAR and Lgi1 can persist despite clinical recovery.