An accessory sacroiliac (SI) joint usually has little clinical significance. However, severe arthritic changes can cause chronic buttock or low back pain and can be misdiagnosed as another disease presenting with sacroiliitis such as ankylosing spondylitis (AS).
A 33-year-old woman was diagnosed with AS due to chronic buttock pain and progressive sacroiliitis on plain X-ray and magnetic resonance imaging (MRI). Her buttock and low back pain gradually worsened despite proper treatment for AS.
Computed tomography revealed an accessory SI joint with arthritic changes.
Nonsteroidal anti-inflammatory drugs (NSAIDs) and restricted movement were prescribed.
The symptoms were controlled with NSAIDs, rest, and restriction of excessive movement. The medication could be stopped after the pain subsided.
An accessory SI joint can be a cause of chronic back pain and can be misdiagnosed as AS with sacroiliitis when progressive arthritic changes are observed. Therefore, additional imaging studies other than conventional X-ray or MRI may be required for accurate diagnosis.
Department of Rheumatology, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University, Seoul, Korea.
Correspondence: Sang-hoon Lee, Department of Rheumatology, Kyung Hee University Hospital at Gangdong, School of Medicine, Kyung Hee University, 892 Dongnam-ro, Gangdong-gu, Seoul 134-727, Republic of Korea (e-mail: firstname.lastname@example.org).
Abbreviations: AS = ankylosing spondylitis, CT = computed tomography, MRI = magnetic resonance imaging, SI = sacroiliac.
Ethics approval was waived due to the retrospective nature of the study. Written informed consent was obtained from the patient for publication of the case.
No specific support was received from any funding bodies in the public, commercial, or not-for-profit sectors to perform the work described in this article.
IRB approval was waived due to the retrospective nature of the study and inclusion of only 1 patient. Written informed consent was obtained from the patient for publication of the case.
The authors have no conflicts of interest to disclose.
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Received November 22, 2018
Received in revised form March 13, 2019
Accepted March 25, 2019