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Key clinical features distinguish peripheral, axial spondyloarthritis
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HILTON HEAD, S.C. — In a duet session focused on spondyloarthritis, Grace Wright, MD, PhD, and Reeti Joshi, MD, detailed the differences between axial and peripheral disease and identified the various features of both in an effort to aid early diagnosis.
“The available evidence suggests a common pathophysiological foundation of SpA as a whole, and thereby supports the concept that SpA is a single disease with a heterogenous phenotype,” Wright, who is president and founder of AWIR, told attendees. “However, we have to understand that we don’t really understand what the underlying pathogenesis is, so it’s hard to make a statement when the foundation doesn’t exist. We have been struggling with understanding this grouping because of many different mechanisms at play. As we dig deeper, thinking through axial vs. peripheral, the discordance and the confusion actually increase even though we are gaining better clarity.”
SpA is common, with 2005 census data demonstrating RA prevalence was 1.3 million while SpA was between 0.6 and 2.4 million. “In medical school, RA was the ‘big thing’ and SpA was that ‘other thing’. These numbers will belie that we were wrong: RA is the big kid on the block because we were just ignoring all the other kids,” Wright said.
What’s more, SpA has a tremendous impact on quality of life and employment, with 49% of patients reporting disability, she said. Additionally, 36% report limitations hindering development of their career and 21% changed, left or lost a job due to SpA. “From an economic and health perspective, this matters because we have to think of holistic approaches to patients and the totality of the impact of their disease and benefits of care.”
Distinguishing features
Hallmarks of peripheral SpA include enthesitis and new bone formation, while uveitis and dactylitis occur in some patients. Enthesitis is important, according to Wright, because it is an early sign of SpA that is often mislabeled. “In women who experience more widespread pain and not local throbbing pain, we often say they have fibromyalgia,” she said. “I’m not going to say it doesn’t exist, but many things are misclassified as fibromyalgia.”
She challenged the audience to think about how many times they see enthesitis or question their diagnosis. It’s a subtle finding, but “if you pick it up early, I think we can do a lot to benefit patients because we know this is one of the primary early lesions and is likely often missed.”
A heterogeneous disease
The heterogeneity of the disease, especially between men and women, poses an additional challenge to diagnosis. Joshi, who is a rheumatologist in Beaumont, Texas, explained that axial SpA (axSpA) usually begins in the third decade of life, with a male-to-female ratio of 2 to 3:1 for ankylosing spondylitis and 1:1 for nonradiographic disease. The proportion of patients with nonradiographic disease are largely similar between axSpA and SpA, she said. However, the condition is often misdiagnosed with RA because around 90% of patients with axSpA report morning stiffness that can last up to 30 minutes, and more than one swollen joint may be present.
Clinical presentations also differ between men and women, making a challenging diagnosis even more complex. For example, Joshi and Wright both acknowledged that women often present with pain in the thoracic spine, neck and chest, and less frequently with lower back pain that is typically seen in men.
Overall, peripheral and axSpA share many similar features, including sacroiliitis, spondylitis, peripheral arthritis, enthesitis, dactylitis, psoriasis, uveitis and IBD. However, key differences set them apart: age of onset (mid-to-late 30s for peripheral vs. early 20s for axSpA); severity and pain (less in peripheral vs. more in axSpA); sacroiliitis (less symmetrical in peripheral vs. more symmetrical in axSpA) and syndesmophytes (less symmetrical in peripheral vs. more symmetrical in axSpA). – by Stacey L. Adams
For more information:
Joshi R, Wright GC. Axial and peripheral SpA: A rheumatic duet. Presented at: AWIR National Conference; August 15-18, 2019; Hilton Head, S.C.
Disclosure: This session was sponsored by Novartis.