Abstract: Objective To report a case of neurosyphilis complicated with Rickettsia felis infection, and summarize the clinical manifestations, cerebrospinal fluid (CSF) and imaging characteristics. Methods and Results A 33-year-old male with a disease course of more than 3 months was admitted to Beijing Tiantan Hospital, Capital Medical University on October 12, 2022, who had kept a cat at home for more than 10 years. The main clinical manifestations were seizure, cognitive function decline, and low fever in the last one month. Serum Treponema syphilis (TP) antibody, Treponema Pallidum Hemagglutination Assay (TPHA), Toluidine Red Unheated Serum Test (TRUST) were positive. CSF test showed increased white blood cell count and protein, positive oligoclonal band, 24 h intrathecal IgG synthesis rate and IgG index. Head MRI showed T₂WI and FLAIR hyperintensity in bilateral medial temporal lobe and hippocampus atrophy, evident on the right side. There were 229 Rickettsia felis sequences and 2 TP sequences detected in CSF metagenomic next-generation sequencing (mNGS). After his medical history was asked again, he was infected with syphilis 7 years ago, and his serum and CSF were positive for TP antibody. The comprehensive clinical and imaging findings were consistent with the characteristics of neurosyphilis, and the fever was consistent with the characteristics of Rickettsia felis infection. He was diagnosed as neurosyphilis complicated with Rickettsia felis infection, who improved after penicillin and doxycycline treatment. Conclusions Neurosyphilis complicated with Rickettsia felis infection is clinically rare. mNGS can help with early diagnosis. Early anti-infective therapy can improve the prognosis.

Key words: Neurosyphilis, Rickettsia felis, Central nervous system infections, Sequence analysis, Cerebrospinal fluid

摘要： 目的 报道1例神经梅毒合并猫立克次体感染患者，并总结其临床表现、脑脊液检查和影像学特点。方法与结果 首都医科大学附属北京天坛医院于2022年10月12日收治1例33岁男性患者，病程3月余，家中养猫10余年。临床主要表现为癫痫发作、认知功能下降，近1个月出现低热。血清梅毒螺旋体抗体阳性，梅毒螺旋体血凝试验阳性，甲苯胺红不加热血清试验阳性；脑脊液白细胞计数增加，蛋白定量升高，寡克隆区带阳性，24小时鞘内IgG合成率和IgG指数升高。头部MRI显示双侧颞叶内侧T₂WI和FLAIR成像高信号，海马萎缩，以右侧显著。脑脊液宏基因组第二代测序技术（mNGS）检出猫立克次体序列数为229条、梅毒螺旋体序列数为2条。追问病史，患者7年前曾患有梅毒，复查血清和脑脊液梅毒螺旋体抗体均呈阳性。综合患者临床和影像学表现，符合神经梅毒特点，发热符合猫立克次体感染特点，临床明确诊断为神经梅毒合并猫立克次体感染，予以青霉素和多西环素治疗后改善。结论 神经梅毒合并猫立克次体感染临床罕见，mNGS有助于早期诊断，尽早抗感染治疗，可以有效改善患者预后。

关键词: 神经梅毒, 猫立克次体, 中枢神经系统感染, 序列分析, 脑脊髓液