Mycobacterium fortuitum infection of the hip joint: a case report and literature review

Osteoarticular infections caused by Mycobacterium fortuitum are exceedingly rare and often result in delayed diagnosis due to nonspecific clinical manifestations. We report a case of septic arthritis of the hip in a 47-year-old man, in which M. fortuitum was identified from synovial fluid by 16S rRNA gene sequencing (99% identity to GenBank reference sequence CP011269.1). Upon definitive diagnosis, antimicrobial therapy was adjusted to intravenous azithromycin and levofloxacin combined with oral trimethoprim-sulfamethoxazole (TMP-SMX). Following clinical improvement, treatment was transitioned to oral azithromycin, levofloxacin, and TMP-SMX for 12 months. At the 18-month follow-up, the patient remained in complete remission without recurrence. This case highlights the critical role of 16S rRNA sequencing in diagnosing non-tuberculous mycobacterial infections and informs therapeutic strategies for similar rare infections.