抗富含亮氨酸的胶质瘤灭活1边缘脑炎（抗LGI1 LE）是最常见的自身免疫性脑炎之一，通常与其他自身免疫性疾病并存。类风湿关节炎（RA）和意义不明的单克隆丙种球蛋白病（MGUS）通常与自身免疫现象相关。然而，迄今为止，RA 和 MGUS 均未在文献中被描述为与抗 LGI1 LE 共存。我们介绍了一名类风湿性关节炎男性患者出现抗 LGI1 LE 的病例，该患者也被发现患有 MGUS。该患者最初接受皮质类固醇和静脉注射免疫球蛋白治疗。轻度复发后，他的治疗辅以利妥昔单抗，导致疾病症状完全消退。我们的报告提供了抗 LGI1 LE 与 RA 和/或 MGUS 共存的证据，从而扩大了患有这些疾病的患者的鉴别诊断表现出提示脑炎的神经精神症状的疾病实体。此外，鉴于缺乏治疗指南及其在病理生理学和临床水平上潜在的相互作用，该病例对这些疾病共存的管理提出了挑战。排除原发性疾病中的传染性脑炎或中枢神经系统受累，还应考虑自身免疫性边缘脑炎 (LE)。对于诊断为抗 LGI1 LE 的患者，应广泛检查是否存在共存的隐匿性癌前病变，即使是当与其他自身免疫性疾病或癌前病变共存时，抗 LGI1 LE 的临床管理和治疗选择可能具有挑战性；因此，需要朝这个方向进行更多研究。© EFIM 2024。

Anti-leucine-rich glioma inactivated 1 limbic encephalitis (anti-LGI1 LE) is one of the most frequent autoimmune encephalitis, commonly coexisting with other autoimmune diseases. Rheumatoid arthritis (RA) and monoclonal gammopathy of unknown significance (MGUS) are commonly associated with autoimmune phenomena. However, neither RA nor MGUS have been described in the literature to date as coexisting with anti-LGI1 LE.We present the case of anti-LGI1 LE in a male patient with rheumatoid arthritis, who was also found to have an MGUS. The patient was initially treated with corticosteroids and IV immunoglobulin. After a mild relapse, his treatment was complemented with rituximab, resulting in complete regression of the disease symptoms.Our report provides evidence for the coexistence of anti-LGI1 LE with RA and/or MGUS, thus extending the differential diagnosis of patients suffering with these disease entities that present with neuropsychiatric symptoms suggestive of encephalitis. Moreover, this case raises challenges on the management of the coexistence of these diseases, given the lack of therapeutic guidelines and their potential interaction on a pathophysiological and a clinical level.In a patient with known autoimmune or malignant background who presents with neuropsychiatric symptoms, after excluding infectious encephalitis or central nervous system involvement in the primary disease condition, autoimmune limbic encephalitis (LE) should also be considered.In a patient diagnosed with anti-LGI1 LE there should be an extensive check for coexisting occult pre-malignant conditions, even for months after disease presentation.Clinical management and treatment options of anti-LGI1 LE when coexisting with other autoimmune or pre-malignant conditions can be challenging; thus, more research is needed towards that direction.© EFIM 2024.