Anti-IgLON5 disease exacerbated by asymptomatic SARS-CoV-2 infection

OBJECTIVE: To report a case of anti-IgLON5 disease unmasked by asymptomatic SARS-CoV-2 infection. BACKGROUND: Anti-IgLON5 disease is a clinically heterogeneous disease that shares features of both neurodegeneration and neuroinflammation. The onset can be insidious, posing diagnostic challenges and often resulting in treatment delay. Infectious trigger was rarely reported in this disease. CASE REPORT: A 64-year-old male initially presented with 1-year history of progressive parasomnia and mild cognitive decline that precipitously worsened over the course of 1 month following asymptomatic SARS-CoV-2 infection, resulting in dysphagia, parkinsonism, weight loss and dependence on all activities of daily living. He was found to have high titer (1:3840) of anti-IgLON5 antibody in the serum, confirming the diagnosis of anti-IgLON5 disease. CONCLUSION: Anti-IgLON5 disease as a potentially reversible cause of neurodegenerative syndrome in patients with atypical features. Timely diagnosis and treatment may improve clinical outcomes. It is also worth noting that symptoms precipitously worsened following SARS-CoV-2 infection. We suspect that a COVID-19-mediated immune activation response exacerbated the underlying autoimmune encephalitis process, unmasking his symptoms.