Mimics of axial spondyloarthritis

An Unusual Mimic of Axial Spondyloarthritis: A Case Report

Axial spondyloarthritis (SpA) is a chronic inflammatory condition predominantly affecting the sacroiliac joints and spine, typically presenting before the age of 45 years with inflammatory back pain. However, diagnostic challenges arise when atypical features and negative autoimmune markers obscure the clinical picture. We present a case of a male in his 40s with no significant medical history, presenting with a three-month history of inflammatory back pain. Despite negative human leukocyte antigen B27 (HLA-B27) status, clinical examination, including positive findings on the FABER (flexion, abduction, and external rotation) test and exaggerated muscle tenderness, raised suspicion of axial SpA. An MRI of the pelvis confirmed bilateral symmetrical sacroiliitis, supporting the diagnosis. Unexpectedly, further investigations revealed a very low vitamin D level, normal calcium levels, and elevated parathyroid hormone (PTH), suggesting secondary hyperparathyroidism. A subsequent PET scan disclosed increased uptake posterior to the right lobe of the thyroid, prompting consideration of secondary hyperparathyroidism due to severe vitamin D deficiency. Treatment with vitamin D supplementation and nonsteroidal anti-inflammatory drugs yielded remarkable improvement in symptoms, with normal repeat blood investigations post-treatment. This case underscores the importance of a comprehensive diagnostic approach in patients with inflammatory back pain, especially when classical markers such as HLA-B27 are negative. It highlights the potential interplay between axial SpA and secondary hyperparathyroidism, emphasizing the need for vigilance and interdisciplinary collaboration in clinical practice.

Differentiating nonradiographic axial spondyloarthritis from its mimics: a narrative review

Background

Optimal treatment of nonradiographic axial spondyloarthritis depends on accurate and timely diagnosis of the underlying disease; however, patients present with common symptoms that, in the absence of radiographic changes, may confound diagnosis.

Methods and findings

In this narrative review, a PubMed literature search was conducted through January 2021, with no date limits, to identify English-language publications discussing classification of nonradiographic axial spondyloarthritis, with an emphasis on clinical features and presentation, differential diagnoses, and mimics of disease. This review describes the epidemiology, clinical features, and burden of disease of nonradiographic axial spondyloarthritis as it relates to the overall axial spondyloarthritis spectrum and discusses mimics and differential diagnoses of nonradiographic axial spondyloarthritis that should be considered when evaluating patients with suspected nonradiographic axial spondyloarthritis in clinical practice.

Conclusions

Recognition of clinical features of nonradiographic axial spondyloarthritis, along with an understanding of comorbid conditions such as fibromyalgia, allows for differentiation from its mimics. Appropriate diagnosis of nonradiographic axial spondyloarthritis is important for aggressive management of disease to reduce pain, avoid loss of function, and improve quality of life.

Clinical Manifestations and Diagnosis of Axial Spondyloarthritis

BACKGROUND

Axial spondyloarthritis (axSpA) is a chronic, rheumatic disease characterized by inflammation of the sacroiliac joint, spine, and entheses. Axial spondyloarthritis affects up to 1.4% of adults in the United States and is associated with decreased quality of life, increased mortality, and substantial health care-related costs, imposing a high burden on patients, their caregivers, and society.

SUMMARY OF WORK

Diagnosing axSpA can be difficult. In this review, we seek to help rheumatologists in recognizing and diagnosing axSpA.

MAJOR CONCLUSIONS

A discussion of challenges associated with diagnosis is presented, including use and interpretation of imaging, reasons for diagnostic delays, differences in disease presentation by sex, and differential diagnoses of axSpA.

FUTURE RESEARCH DIRECTIONS

The early diagnosis of axSpA and advances in available therapeutic options have improved patient care and disease management, but delays in diagnosis and treatment remain common. Additional research and education are critical for recognizing diverse axSpA presentations and optimizing management early in the course of disease.

Osteitis condensans ilii in a patient with ulcerative colitis: a mimic of ankylosing spondylitis or non-radiographic axial spondyloarthritis

Osteitis condensans ilii (OCI) is known as one of the sacroiliitis diseases and the symptoms or radiographic findings of OCI sometimes resembled those of ankylosing spondylitis (AS) of non-radiographic axial spondyloarthritis (nr-axSpA). Bone marrow edoema (BME) around sacroiliac (SI) joints on magnetic resonance imaging (MRI) is one of the key findings in the classification criteria of axial SpA, but BME on MRI was also found in patients with OCI. The usage of SI joint MRI is increasing due to the need of accurate or early diagnosis of axial SpA in accordance with development of new biological treatments. Here was the case of a 38-year-old female patient with ulcerative colitis (UC) complicated with OCI, which was a mimic of AS or nr-axSpA. She had a persistent low back pain with BME around SI joints on MRI. She could meet the ASAS criteria of axial SpA and might be diagnosed with inflammatory bowel disease (IBD) related axial SpA. OCI is not a rare disease as a differential diagnosis for axial SpA especially in young women. We report this case with a literature review of OCI and would like the clinicians to be aware of the disease when diagnosing AS or nr-axSpA with chronic low back pain.

How to investigate: Early axial spondyloarthritis

Axial spondyloarthritis (axSpA) is a chronic inflammatory condition of the axial skeleton that encompasses radiographic and non-radiographic axSpA and that can lead to chronic pain, structural damage, disability, and loss of quality of life. Scientific advances, including the role of MRI assessment, have led to new diagnostic insights and the creation of a new set of classification criteria for axial and peripheral SpA. New criteria allow the identification of SpA patients with early disease and their enrolment in clinical studies. In this chapter, we discuss the difference between diagnostic and classification criteria, the diagnostic approach to patients with suspected axSpA, the limitations of MRI assessment, and the importance of early identification of this condition. A practical algorithm to investigate axSpA, based on the current evidence, is also proposed. Clinical judgement should always be kept as the mainstay in the diagnosis of axSpA.