Abstract
The serum phenylalanine (Phe)/tyrosine (Tyr) ratio has recently been described as a potential prognostic biomarker for anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis in adulthood; however, little is known about this phenomenon among children. As such, this study aimed to identify the characteristics of Phe and Tyr metabolism and specific immune cell subsets in children diagnosed with anti-NMDAR encephalitis. Clinical data from 24 patients diagnosed with anti-NMDAR encephalitis at the Capital Center for Children's Health, Capital Medical University, between January 2019 and March 2022, were retrospectively analyzed. Among children with anti-NMDAR encephalitis, blood levels of Tyr were decreased in those with sleep disorders and decreased consciousness. Blood Tyr levels and Phe/Tyr ratios were significantly associated with disease severity. In addition, the percentage of B lymphocytes was increased in patients with anti-NMDAR encephalitis, and there was a strong correlation between blood Tyr level, Phe/Tyr ratio, and the percentage of B lymphocytes. Furthermore, significant correlations were found between blood Tyr levels, Phe/Tyr ratio, percentage of B lymphocytes, and modified Rankin Scale and Glasgow Coma Scale scores. CONCLUSION: Blood Phe and Tyr levels and lymphocyte subsets differed among children diagnosed with anti-NMDAR encephalitis. Blood levels of Tyr and the Phe/Tyr ratio were associated with the severity of neurological status and percentage of B lymphocytes. These findings highlight the importance of interactions between metabolism and immunity and their effects on neuronal function in the brain. WHAT IS KNOWN: • Elevated serum phenylalanine (Phe)/tyrosine (Tyr) ratio is associated with psychiatric syndrome and the severity of anti-NMDAR encephalitis in adulthood. • T lymphocyte subsets in the cerebrospinal fluid were different between adults with anti-NMDAR encephalitis and those with viral encephalitis. WHAT IS NEW: • Blood Tyr levels were decreased in anti-NMDAR encephalitis children with sleep disorders and decreased consciousness and were significantly associated with disease severity. • The percentage of B lymphocytes was increased in children with anti-NMDAR encephalitis, with a significant correlation between blood Tyr level, Phe/Tyr ratio, and the percentage of B lymphocytes.