Systemic lupus erythematosus complicated by refractory Mycobacterium avium complex infection involving bilateral lower extremities: a case report and literature review.

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.