Re: Concomitant Bilateral Sacroiliitis and Lumbar Spondylodiscitis Secondary to Staphylococcus aureus Sepsis

Dear Editor,

We read with great interest the case report by Gözdaş and Hızal describing Staphylococcus aureus bacteremia complicated by concomitant bilateral sacroiliitis and lumbar spondylodiscitis.¹ The authors are to be commended for presenting this rare co-occurrence, as infectious sacroiliitis remains a diagnostic challenge due to its nonspecific clinical presentation and frequent overlap with inflammatory spondyloarthritis. In this regard, magnetic resonance imaging (MRI) may help distinguish infectious from inflammatory sacroiliitis: infectious cases typically show asymmetric bone marrow edema, periarticular soft-tissue inflammation, and occasionally abscess formation, whereas inflammatory sacroiliitis tends to present with symmetric involvement and chronic structural lesions.²

The manuscript has notable strengths. First, the detailed radiological documentation (lumbar and pelvic MRI) provides convincing visual evidence supporting the dual infectious process. Second, the longitudinal follow-up showing radiological regression after a six-month antibiotic course contributes valuable information to clinicians regarding prognosis and recovery expectations. Finally, by reporting S. aureus as the etiologic agent in a bilateral presentation, the study highlights the need to maintain vigilance for metastatic foci even in immunocompetent individuals. This presentation, while rare, is consistent with other reported cases of bilateral infectious sacroiliitis secondary to S. aureus bacteremia, further underscoring the importance of its early recognition in clinical practice.

Nevertheless, a few aspects merit further consideration:

1. Microbiological confirmation — While blood cultures confirmed S. aureus, joint aspiration or biopsy could have provided stronger local diagnostic confirmation, especially since sacroiliac involvement is uncommon in hematogenous spread.

2. Differential diagnosis — The discussion would have benefited from a brief comparison with inflammatory sacroiliitis (e.g., human leukocyte antigen B27-negative [HLA-B27–negative] axial spondyloarthritis), emphasizing key distinguishing features in MRI signal patterns and clinical evolution.

3. Treatment details — The rationale for continuing ampicillin–sulbactam for one month before switching to oral amoxicillin–clavulanate could have been elaborated, particularly in the context of methicillin-sensitive S. aureus, where anti-staphylococcal penicillins or cefazolin are preferred in current guidelines.²

4. Functional outcomes — Quantitative functional scores (such as the Bath Ankylosing Spondylitis Functional Index or a pain visual analog scale) would have enriched the assessment of post-treatment recovery.

Despite these limitations, the case elegantly illustrates that S. aureus bacteremia can lead to simultaneous spondylodiscitis and bilateral sacroiliitis, expanding our understanding of the infection’s metastatic potential. The report serves as a timely reminder to include infectious etiologies in the differential diagnosis of acute-onset back or gluteal pain, even in the absence of typical risk factors. This message is especially relevant in routine clinical practice, where early radiological assessment and microbiological evaluation play a crucial role in preventing diagnostic delay and ensuring optimal outcomes.

Conflict of Interest

The author has no conflicts of interest to declare.

Financial Disclosure

The author declares that this study received no financial support.

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Peer-review

Externally peer-reviewed.