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Ankylosing Spondylitis & Related Diseases Information
Undifferentiated Spondyloarthropathy (USpA): Quick Links
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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 unrecognized by many physicians. Sometimes a doctor may make an initial diagnosis of "Spondyloarthropathy" or "Unclassified Spondyloarthopathy" if certain symptoms are present, but are not enough to make a specific diagnosis. Sadly, patients with USpA may initially hear that they are "anxious and depressed" or receive a diagnosis of fibromyalgia, which is a chronic disorder associated with widespread muscle and soft tissue pain.

A person with USpA may have signs and symptoms of spondylitis that do not quite fit into a specific category. For example, someone may have (or experienced) iritis and heal pain, as well as be HLA-B27 positive, but initially not have the SI joint or spinal involvement associated with ankylosing spondylitis.

A rheumatologist is commonly the type of physician that will diagnose USpA, since they are doctors who are specially trained in diagnosing and treating disorders that affect the joints, muscles, tendons, ligaments connective tissue, and bones. A diagnosis of USpA normally comes after a physical exam, laboratory tests and x-rays.

Differences in Diagnostic Criteria Between Ankylosing Spondylitis and Undifferentiated Spondyloarthropathy:

  • HLA-B27 Gene Test: The diagnostically helpful tissue type gene called HLA-B27, seen in over 95% of people with ankylosing spondylitis, is commonly absent in undifferentiated spondyloarthropathy. Approximately only 20-25% of people with USpA test positive for HLA-B27.

  • X-rays: While x-ray of the pelvis region (where the sacroiliac joint is located) is essential for diagnosis in AS, subtle erosions do not always show in x-rays of undifferentiated spondyloarthropathy patients.

  • Symptoms of inflammatory spinal pain are the first clues of AS, which is not necessarily the case in people with undifferentiated spondyloarthropathy. However, oftentimes women with any form of spondylitis feel primary pain in a different area of the body than the spine or low back. Some experts suggest that a misdiagnosis of fibromyalgia is sometimes made in women with undifferentiated spondyloarthropathy, who present with diffuse muscle aches and pains, without any measurable lab or x-ray abnormalities. This hypothesis was supported by studies published in 1998 in the American Journal of Medicine and the Archives of Internal Medicine.

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