Anti-dipeptidyl-peptidase-like protein 6 encephalitis with pure cerebellar ataxia: a case report

BACKGROUND: Anti-dipeptidyl-peptidase-like protein 6 (DPPX) encephalitis is a rare autoimmune encephalitis. The clinical symptoms of anti-DPPX encephalitis are often severe, manifested as diarrhea/weight loss, central nervous system hyperexcitability and cognitive dysfunction. CASE PRESENTATION: An 18-year-old boy was admitted for 1-week-long cerebellar symptoms including dizziness, unsteady gait and frequent vomiting. Magnetic resonance imaging (MRI) displayed no abnormal findings. However, autoimmune encephalitis panel revealed anti-DPPX antibody was positive in the serum. This patient completely recovered after immunoglobulin and corticoids therapy. In addition, repeat serum antibody test for DPPX was negative within one month. CONCLUSION: In addition to the classic triad, anti-DPPX encephalitis may manifest as mild and rare symptoms due to lower antibody titers. Fast identification of rare symptoms can help to quickly diagnosis and effective treatment.