An unexpected cause of sacroiliitis in a patient with gout and chronic psoriasis with inflammatory arthritis: a case report.

BACKGROUND: Inflammatory back pain is a condition characterized by inflammation of the sacroiliac joints and lower spine. It is frequently seen in patients with spondyloarthropathies like ankylosing spondylitis, psoriatic arthritis, enteropathic arthritis and reactive arthritis. Inflammatory back pain can be caused by many other conditions like infection and crystal deposition such as gout. In this case, it is difficult to specifically identify gout as a cause by ordinary imaging like magnetic resonance imaging (MRI) or ultrasound.

CASE PRESENTATION: This case report describes a young man with severe psoriasis, presumptive psoriatic spondyloarthropathy and chronic extensive tophaceous gout which was difficult to treat because of non-compliance with medications and lifestyle. He presented with inflammatory type low back and buttocks pain with raised inflammatory markers. MRI of the lower back and sacroiliac joints showed features of active sacroiliitis. He was subsequently treated with a Tumor Necrosis Factor (TNF) alpha inhibitor for presumed axial psoriatic arthritis and had no significant benefit. Two attempts DECT of the lumbar spine was not executed correctly. CT lumbar spine and SIJs showed L2/3 endplate and left SIJ erosions mostly related to gout. Rasburicase was introduced. The tophi decreased in size peripherally with marginal improvement in back pain. From this study, we want to bring to the attention of physicians that gout can lead to back pain with inflammatory changes on MRI. We also want to address the importance of other imaging modalities if the cause of the back pain is not clear.

CONCLUSION: This case is meant to highlight an important but overlooked cause of active sacroililitis and inflammatory type back pain in patients who have gout, and to bring to the attention that plain X-ray, MRI and ultrasound cannot differentiate between inflammatory sacroiliitis caused by seronegative arthritis versus gouty arthritis. CT scan can add more information but DECT is the preferred method for differentiation and identification of axial tophaceous gout.