Intractable nausea and vomiting from autoantibodies against a brain water channel.

BACKGROUND & AIMS: Antibodies against the water channel protein aquaporin (AQP)-4 cause a spectrum of inflammatory, demyelinating, central nervous system disorders called neuromyelitis optica spectrum disorders (NMOSDs); these primarily affect the optic nerves and spinal cord but also the brain. Symptoms of intractable nausea, vomiting, and hiccups reflect involvement of AQP4 in the brainstem area postrema and account for gastroenterological presentations. We investigated the frequency of intractable nausea, vomiting, or hiccups in patients with NMOSD who tested positive for immunoglobulin G against AQP4 (AQP4-IgG). We also analyzed sera from patients with idiopathic nausea or vomiting for the presence of AQP4-IgG.
METHODS: We reviewed the Mayo Clinic AQP4-IgG positive NMOSD database (n = 70) to identify patients who presented with vomiting, focusing on results from gastroenterological evaluations. We also tested serum samples (from the Gastroparesis Clinical Research Consortium repository) from patients who presented with idiopathic nausea or vomiting for AQP4-IgG (controls, n = 318 with gastroparesis and 117 without gastroparesis).
RESULTS: Ten AQP4-IgG-positive patients diagnosed with NMOSD (14% of patients in the database) initially presented with intractable vomiting. Extensive gastroenterological evaluation was noninformative. AQP4-IgG was not detected in any of the controls.
CONCLUSIONS: Although NMOSDs are rare, tests for AQP4-IgG should be considered for patients who present with unexplained, intractable vomiting. Detection of the antibody before the development of optic neuritis or transverse myelitis allows patients to receive immunosuppressive therapy before the development of neurologic disabilities.