Multiple Deep Abscesses Caused by Disseminated Nocardia farcinica Infection After Immunosuppressive Treatment for Membranous Nephropathy: A Case Report and Literature Review.

Nocardia farcinica is a highly virulent opportunistic pathogen with a marked propensity to cause disseminated infection in immunocompromised hosts. Its clinical manifestations are often nonspecific, conventional empirical anti-infective therapy may be ineffective, and both misdiagnosis and mortality rates remain high. We report the case of a 20-year-old man with membranous nephropathy who developed multiple cutaneous and deep soft-tissue abscesses, fever, and pulmonary infiltrates after 7 months of dual immunosuppressive therapy with methylprednisolone and tacrolimus. Initial empirical treatment with oxacillin plus moxifloxacin failed to control the infection, and the patient continued to experience high fever with persistently elevated inflammatory markers. Direct smear examination of pus specimens showed weakly acid-fast, branching filamentous organisms, and culture followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) identified the pathogen as Nocardia farcinica. According to antimicrobial susceptibility testing, therapy was adjusted to trimethoprim-sulfamethoxazole (SMZ-TMP) combined with amoxicillin/clavulanate potassium. The patient subsequently became afebrile, the abscesses gradually decreased in size, and inflammatory markers improved substantially. After clinical stabilization, he was discharged on continued oral anti-infective therapy and showed no evidence of recurrence during 12 months of outpatient follow-up. Together with a review of the literature, this report discusses the clinical features, etiological diagnostic strategies, and susceptibility-guided anti-infective regimens for disseminated Nocardia farcinica infection in immunosuppressed patients, with the aim of providing a practical reference for clinical diagnosis and treatment.