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. What this paper adds Māori and Pacific Island children are at increased risk of anti‐N‐methyl‐d‐aspartate (NMDA) receptor encephalitis (3.4 and 10.0 per million children per year respectively). One third of Māori and Pacific Island children with anti‐NMDA receptor encephalitis have a poor outcome. This article is commented on by Njafang and Missa on page 673 of this issue. Video Podcast: https://youtu.be/0ZDY574Mr6Q