Anti-NMDA-receptor encephalitis and concurrent neuroborreliosis misdiagnosed for post-COVID-19-syndrome: a case report.

We present a case of a 42-year-old woman with paraneoplastic anti-N-Methyl-D-Aspartat (NMDA)-receptor encephalitis and concurrent neuroborreliosis that was initially misdiagnosed as post-COVID-19 syndrome. Clinically, the patient presented with a range of chronic and subacute neuropsychiatric symptoms and recalled a tick bite weeks prior to admission. The patient had undergone psychiatric and complementary medical treatments for 1 year before admission and was initially diagnosed with post-COVID-19 syndrome. Admission was performed because of acute worsening with fever, confusion, and unsteady gait. Cerebrospinal fluid (CSF) analysis revealed pleocytosis with elevated borrelia Immunoglobulin M (IgM) and Immunoglobulin M (IgG) CSF/blood antibody indices, indicating acute neuroborreliosis. Anti-NMDA receptor antibodies were identified in the CSF a cell-based assay and were confirmed by an external laboratory. Other paraneoplastic antibodies were ruled out during in-house examination. Cranial Magnetic resonance imaging (MRI) revealed basal meningitis, rhomb- and limbic encephalitis. A subsequent pelvic Computer tomography (CT) scan identified an ovarian teratoma. The patient's clinical condition improved dramatically with antibiotic treatment and plasmapheresis, the teratoma was surgically removed and she was started on rituximab. Our case highlights that amidst the prevailing focus on COVID-19-related health concerns, other well-established, but rare neurological conditions should not be neglected. Furthermore, our case illustrates that patients may suffer from multiple, concurrent, yet pathophysiologically unrelated neuroinflammatory conditions.