Perinephritic and psoas abscess by an unusual coinfection with Trichomonas vaginalis and Lactobacillus johnsonii.

Trichomoniasis, caused by Trichomonas vaginalis, is a common nonviral sexually transmitted infection that presents with vaginitis, urethritis, cystitis, prostatitis, and rarely perinephric abscess. Here we presented a 49-year-old female with fever and lumbago diagnosed with a coinfection of perinephric and psoas abscess caused by Lactobacillus johnsonii and T. vaginalis, with the etiological diagnosis established using pus culture and metagenomic next-generation sequencing (mNGS). The patient achieved complete recovery following abscess drainage, incision, and combined therapy with metronidazole and piperacillin/tazobactam. Rare manifestations of trichomoniasis are easily misdiagnosed, and mNGS can help identify T. vaginalis quickly and accurately without prediction.