Anti-mGluR5 encephalitis: distinctive clinical features and antibody patterns in the Chinese population.

Background: Anti-metabotropic glutamate receptor 5 (mGluR5) encephalitis is a rare subtype of autoimmune encephalitis, most often associated with Hodgkin's lymphoma, and accounts for less than 1% of reported cases worldwide. Current knowledge is primarily based on isolated reports from Western populations, with limited data from Asia. The clinical spectrum, tumor associations, and antibody detection patterns in Chinese patients remain poorly understood. Methods: We retrospectively reviewed eight consecutive patients with anti-mGluR5 encephalitis diagnosed at a single tertiary referral center between October 2019 and March 2025. Demographic, clinical, neuroimaging, antibody testing, treatment, and outcome data were analyzed. In addition, a systematic review of the Chinese literature identified 31 previously reported cases. Combined institutional and literature cases (n = 39) were summarized and contextualized within the existing international literature. Results: The age at onset was 42.5 ± 19.7 years (range: 7-78), with a male-to-female ratio of 8:5. Cognitive impairment (61.5%) was the most frequent presenting feature, followed by behavioral disturbances (53.8%) and seizures (53.8%). Tumors were identified in only 7.7% of Chinese patients, notably lower than the 61.5% reported in international literature, with Hodgkin's lymphoma rarely observed in this population. Serum anti-mGluR5 antibodies were detected in all tested patients, while cerebrospinal fluid positivity was observed in 42.4% of paired samples. First-line immunotherapy (steroids, intravenous immunoglobulin, or plasma exchange) led to clinical improvement in most patients, with 89.5% achieving a favorable outcome (Modified Rankin Scale ≤ 2) at last follow-up. Decreased consciousness at onset was significantly associated with a poorer prognosis (p = 0.009). Conclusions: Chinese patients with anti-mGluR5 encephalitis exhibit distinctive clinical and immunological features, particularly in terms of tumor associations and antibody detection patterns. These findings expand our understanding of population-specific characteristics in anti-mGluR5 encephalitis and underscore the need for tailored diagnostic strategies and early immunotherapy to optimize outcomes.