NMDAR encephalitis may be more common among non-Caucasians. A population-based study was conducted to estimate its incidence in Sabah, Malaysia, where the population consists predominantly of Austronesians (84%), and with a Chinese minority. Registries of NMDAR encephalitis at neurology referral centers were reviewed for case ascertainment. The annual incidence was 2.29/million (Austronesians: 2.56/million, Chinese: 1.31/million). Among pediatric population, the incidence was: Austronesians: 3.63/million, Chinese: 2.59/million. Our study demonstrated a higher incidence of NMDAR encephalitis among Austronesians than the predominantly Caucasian populations in Europe (0.5-0.9/million; pediatric: 0.7-1.5/million). Racial and genetic factors may contribute to risks of developing NMDAR encephalitis.
Anti-N-Methyl-D-Aspartate receptor (NMDAR) encephalitis is an immune mediated condition, which remains relatively unknown in Malaysia outside tertiary hospitals with neurology unit. It is often misdiagnosed as a psychiatric illness before definitive treatment is instituted. We report here an 18-year-old man who initially presented to the psychiatry unit before he was subsequently diagnosed as having anti-NMDAR encephalitis. To our knowledge, this is the first reported case of anti-NMDAR encephalitis in the east coast of Peninsular Malaysia.