Yuanyuan Liu, Yulin Liu, Shengxun Huang, Yanan Zhao, Li Zhu, Tiantian Wang, Hongbin Liang, Mengliu Liu, Wei Geng
Background Patients with systemic lupus erythematosus (SLE) receiving long-term glucocorticoids and immunosuppressants are at markedly increased risk of opportunistic infections. Mycobacterium avium complex (MAC) is a common nontuberculous mycobacterial pathogen, but MAC osteomyelitis is extremely rare in non-HIV SLE patients, posing diagnostic and therapeutic challenges. Case presentation We report a 52-year-old female with SLE on long-term prednisone, azathioprine, leflunomide, and hydroxychloroquine, who developed bilateral tibial and femoral osteomyelitis complicated by soft tissue abscesses, drug-induced dermatitis, and severe malnutrition. Conventional microbiological tests remained negative. Metagenomic next-generation sequencing (mNGS) of lower-extremity secretions and pus identified MAC. She underwent five surgical debridements and prolonged multidrug antimycobacterial therapy (azithromycin, rifampicin, ethambutol, amikacin), along with nutritional support and immunosuppressant adjustment. The infection was controlled with no SLE flare, and she recovered favorably. Conclusion Disseminated MAC osteomyelitis can occur in SLE patients under sustained immunosuppression even during disease remission. mNGS enables rapid pathogen identification and is crucial for diagnosing complicated infections. Management requires combined surgical debridement, prolonged antimycobacterial therapy, and multidisciplinary care.