Anti‐N‐methyl‐d‐aspartate receptor encephalitis in Māori and Pacific Island children in New Zealand

Aim To investigate the incidence and severity of anti-N-methyl-d-aspartate (anti-NMDA) receptor encephalitis in children from New Zealand. Method A retrospective case series was undertaken of all children (≤18y) diagnosed with anti-NMDA receptor encephalitis from January 2008 to October 2015. Results Sixteen patients were identified with anti-NMDA receptor antibodies in the cerebrospinal fluid, three of whom had an associated teratoma. Fifteen children had Māori and/or Pacific Island ancestry. The incidence of anti-NMDA receptor encephalitis in Māori children was 3.4 per million children per year (95% confidence interval [CI] 1.4–7.0) and the incidence in Pacific children was 10.0 per million children per year (95% CI 4.3–19.8) compared with 0.2 per million children per year (95% CI 0.0–1.0) in children without Māori or Pacific Island ancestry. Sixty-seven per cent of children had a good outcome (modified Rankin Score ≤2) at 2 years’ follow-up. This compares unfavourably with other cohorts despite a shorter median time to first-line immunotherapy (13d; range 4–89) and a higher proportion of children being treated with second-line therapy (50%). Interpretation Māori and Pacific Island children have a higher incidence of anti-NMDA receptor encephalitis and possibly a more severe phenotype. These data suggest a genetic predisposition to anti-NMDA receptor encephalitis in these populations.