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Overview of Undifferentiated Spondyloarthritis

Undifferentiated spondyloarthritis (USpA) is a term used to describe symptoms and signs of spondylitis in someone who does not meet the criteria for a definitive diagnosis of AS or a related disease. Sometimes a doctor may make an initial diagnosis of "spondyloarthritis" or "unclassified spondyloarthritis" if certain spondylitis symptoms are present but are not distinctive enough to make a specific diagnosis. 

For example, an adult may have iritis, heel pain (enthesitis), and knee swelling, WITHOUT back pain, psoriasis, a recent infection, or intestinal symptoms. This person’s combination of disease features suggests spondyloarthritis, but they don’t neatly fit into the categories of ankylosing spondylitis, psoriatic arthritis, reactive arthritis, juvenile spondyloarthritis, or enteropathic arthritis. Over time, some people with USpA will develop a more well-defined form of spondylitis such as ankylosing spondylitis.

Many people with USpA have been told over the years that they are simply "anxious and depressed" or received a diagnosis of fibromyalgia, a chronic disorder associated with widespread muscle and soft tissue pain.

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According to Dr. Herbert Kaplan, MD (retired) pain may be the only complaint of people with undifferentiated spondyloarthritis. Some people with undifferentiated spondyloarthritis later develop symptoms of the other forms of spondylitis, such as ankylosing spondylitis (AS) or psoriatic arthritis, while others will continue to have chronic, but generally not severe symptoms, and remain "undifferentiated."

Learn More About Symptoms


Undifferentiated spondyloarthritis (USpA) is reportedly the most difficult disease to diagnose in the spondylitis family and consequently eludes a correct diagnosis in many patients who have it. USpA is the least well known of the group and is still unrecognized by some physicians.

Learn More About Diagnosis

Is There a Cure?

Currently, there is no known cure for USpA, but there are treatments and medications available to reduce symptoms and manage the pain.

Learn More About Treatments

Disease Course/Prognosis

Patients with USpA generally have a good prognosis, but over time, some may develop AS or a related disease. Some experts believe that those who test positive for the HLA-B27 genetic marker are more likely to develop AS after initially being diagnosed with undifferentiated spondyloarthritis.

A minority of people with USpA will have mild and intermittent symptoms requiring only symptomatic therapy, but many will have chronic, though not severe, symptoms requiring regular treatment and medication.

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