N-methyl-D-aspartate receptor antibody-associated movement disorder without encephalopathy.

N-methyl-D-aspartate receptor (NMDAR) antibody encephalitis is a well-recognized clinico-immunological syndrome that presents with a movement disorder, cognitive decline, psychiatric symptoms, and epileptic seizures. A pure monosymptomatic presentation is rare; however, some patients present predominantly with a movement disorder in the absence of encephalopathy. Here, we describe three paediatric patients with an NMDAR antibody-mediated movement disorder: a 5-year-old female with acute onset hemichorea, a 10-year-old female with generalized chorea, and a 12-year-old male with abdominal myoclonus. These patients did not develop the characteristic encephalopathy syndrome seen in NMDAR encephalitis, but all three had other associated subtle cognitive deficits. The patients demonstrated good responses to immunotherapy.