Neurosyphilis complicated with Rickettsia felis infection: one case report and literature review

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, 24h 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 2TP 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.

Keywords

• neurosyphilis
• rickettsia felis
• central nervous system infections
• sequence analysis
• cerebrospinal fluid