Four-Year Course of Serum and Cerebrospinal Fluid Antibody Titers in a Patient with Anti-NMDAR Encephalitis

The natural long-term course of antibody titers in patients with anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis remains uncertain. We measured anti-NMDAR antibodies in a patient with anti-NMDAR encephalitis who had a severe disease course for 5 years. The antibody titers in the first serum and cerebrospinal fluid (CSF) samples were 1:1600 and 1:320, respectively. During gradual recovery, the serum and CSF titers initially decreased, but remained unchanged during the last 2 years. Four years after the onset of disease, the serum and CSF antibody titers were 1:200 and 1:80, respectively. Anti-NMDAR antibodies can persist for prolonged periods in patients with a poor clinical course.