Abstract
Anti-dipeptidyl-peptidase-like protein 6 (DPPX) antibody-mediated disease is a rare autoimmune encephalitis which typically presents with a triad of diarrhoea and/or weight loss, central nervous system hyperexcitability and cognitive dysfunction.
We report the case of a 16-year-old female presenting with binocular diplopia and ataxic gait in the context of recent mood disturbance with concurrent psychosocial stressors, poor appetite and significant weight loss. She was empirically treated with thiamine for presumed Wernicke’s encephalopathy. Initial examination demonstrated hyperekplexic neurologic syndrome with startle myoclonus and cervical tremor, dysconjugate mixed horizontal and torsional nystagmus, ocular flutter and global hyperreflexia with flexor plantar responses. Magnetic resonance imaging (MRI) brain/orbits and initial cerebrospinal fluid (CSF) analysis were unremarkable. Weak granular staining detected on CSF immunofluorescence then prompted anti-DPPX antibody testing, which returned strongly positive. The patient was treated with intravenous methylprednisolone and immunoglobulin. There was notable improvement in the cervical tremor and ataxia, however, the ocular flutter and nystagmus persisted. There has been no neurological progression over a six-month follow up period.
This case highlights a variation in clinical presentation of anti-DPPX antibody syndrome. On review of the literature, most cases are associated with gastrointestinal symptoms and encephalitis. In our patient, other than weight loss, there were no reported gastrointestinal upset and no clear cognitive dysfunction. Cases of anti-DPPX associated ocular flutter and nystagmus have rarely been described. It is important to consider this disorder in the differential diagnosis of the well-known entity of Wernicke’s encephalopathy given the phenotypic overlap of anorexia, weight loss, nystagmus and ataxia.
