DPPX antibody-associated encephalitis: A short report on a Chinese patient

DPPX encephalitis, an ancillary, regulatory protein of the Kv4.2 potassium channel Dipeptidyl-peptidase-like protein-6, is caused by cell surface autoantigens to DPPX, and is considered a rare but treatable autoimmune disease. Patients generally start with gastrointestinal symptoms (diarrhea and abdominal pain) or weight loss, and then precede the central nervous system (CNS) hyperexcitability with or without cognitive dysfunction. Here we reported a DPPX-associated patient, whose titer of DPPX antibody was inconsistent with clinical symptoms. This study presents a case exhibiting mild symptoms of DPPX encephalitis. A 30-year-old male suffered from mild memory loss after a fever, which could be easily misdiagnosed as influenza or other common diseases. Immunological examination based on cell-based assay (CBA) detected DPPX antibody in both cerebrospinal fluid and serum. All the symptoms recovered after the administration of immunotherapy within 3 weeks. The DPPX titer in serum, however, became higher at the same time. Six months later, the re-examination of the cerebrospinal fluid immunological test was negative for the DPPX antibody. In view of the symptoms of DPPX-associated encephalitis and the fact that changes in antibody titers in CSF are more likely to reflect symptomatic changes, we suggest that clinicians actively perform lumbar puncture in suspected patients to avoid misdiagnosis or misjudgment of the disease.