Unmasking the Hidden Culprit: Rare Cases of Sacroiliac Joint Inflammation Beyond Spondyloarthritis

Abstract

Inflammatory sacroiliitis can commonly be met in rheumatology practice but is very often underdiagnosed due to poor assessment of sacroiliac joints. This case series discusses three rare entities where the bilateral and symmetric sacroiliac joint disease occurred; all three were not ankylosing spondylitis, Crohn's colitis, ulcerative colitis, psoriatic arthritis, or reactive arthritis. It will attempt to provide an emphasis on proper evaluation, correct diagnosis, and sacroiliac joint imaging in such patients. To emphasize the much-needed improvements in techniques for diagnosis and more prevalent awareness among healthcare professionals, this case study focuses on the less common causes of sacroiliitis.

Introduction

Inflammatory sacroiliitis is an important condition, often inappropriately overlooked in the field of rheumatology. The sacroiliac joint (SIJ), which is located at the union of the spine and the pelvis, is involved in spondyloarthritis quite frequently, an underdiagnosed disease because of inadequate evaluation. A diagnosis of sacroiliitis between ages 12 and 45 years can be considered very indicative of spondyloarthritis with no evidence of infection or crystal-induced arthritis. Most patients suffering from such conditions as fibromyalgia go through unnecessary misdiagnoses, especially when serological tests return negative.

This case series is a review of three unique presentations of bilateral and symmetric SIJ disease that are unrelated to more common conditions such as ankylosing spondylitis or inflammatory bowel diseases like Crohn's colitis. This study is especially pointing out the importance of clinical evaluation and SIJ imaging in the identification and treatment of these inflammatory joint diseases.

Patient Information

Three patients in the rheumatology clinic complained of chronic low back pain, morning stiffness, and intermittent buttock pain aged between 30 and 45 years. The patients did not have any of the known diagnoses of common inflammatory arthritis. The patients also had negative serologies for all markers of ankylosing spondylitis, rheumatoid arthritis, and psoriatic arthritis. They also had a test to rule out infections and metabolic diseases. Despite a lack of these common markers, the clinical signs in all three patients persist.

Clinical Findings

The primary clinical findings in all three patients included:

1. Chronic low back pain lasting more than six months

2. Morning stiffness lasting longer than 30 minutes

3. Bilateral buttock pain exacerbated by physical activity

4. Normal blood markers for common rheumatologic conditions such as rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies

5. Absence of HLA-B27, often associated with ankylosing spondylitis

6. No signs of inflammatory bowel disease or psoriatic lesions

Timeline

The patients had experienced symptoms for several years before presentation at the clinic, with worsening over the past 12 months. Initially, they were misdiagnosed with mechanical low back pain or fibromyalgia and were given non-specific treatments, such as physical therapy and over-the-counter pain medication, which provided little relief.

Diagnosis

Each patient underwent imaging studies, including MRI and CT scans of the sacroiliac joints. The following findings were noted:

1. Bilateral and symmetric sacroiliac joint involvement

2. Evidence of joint space widening, cortical irregularities, and bone marrow edema

3. SIJ fusion in one patient, indicating the chronicity of the disease

4. Despite the absence of typical inflammatory markers, these imaging findings were consistent with inflammatory sacroiliitis.

Follow-up and Outcome

Following proper diagnosis, patients were treated with targeted therapies, including non-steroidal anti-inflammatory drugs (NSAIDs) and disease-modifying antirheumatic drugs (DMARDs). Two of the patients responded well to the treatment and reported significant improvement in pain and mobility within six months of follow-up. The third patient, whose disease had progressed to joint fusion, showed a more modest improvement.

Discussion

These cases contradict the perception that sacroiliitis represents diseases such as ankylosing spondylitis and inflammatory bowel disease. The lack of common serological markers, in combination with clinical presentation and imaging findings, underscores the need for a careful assessment of SIJ involvement in patients with chronic low back pain and morning stiffness.

One of the important observations is that the disease of SIJ, particularly in its early stages, can sometimes be mistakenly equated with mechanical back pain or fibromyalgia, leading to delayed or even inappropriate treatment. Providers must always keep a high index of suspicion when considering SIJ imaging, particularly MRI, as it is much more sensitive in revealing early signs of inflammatory changes than conventional X-rays.

Patient Perspective

Each patient expressed relief at finally receiving a correct diagnosis after years of mismanagement. One patient noted, "I thought I would never get answers. The MRI changed everything, and finally, I got the treatment that worked." Another stated, "I was told it was all in my head or just muscle pain. Having a clear diagnosis made me feel validated."

These perspectives highlight the importance of accurate diagnosis and patient education in managing inflammatory sacroiliitis.

Conclusion

This case study highlights the importance of establishing inflammatory sacroiliitis as a distinct clinical entity that might be overlooked unless a proper evaluation is considered. Although these conditions are rare, the providers should pay more attention so that increased awareness is attained. SIJ imaging, especially MRI, should be included in the diagnostic work-up in patients with chronic low back pain, morning stiffness, or unexplained buttock pain in whom routine serological markers have returned negative. Early diagnosis and targeted therapy may thus greatly improve the outcome of a patient's life.

References

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