To identify objective features individualizing spondyloarthropathy with isolated entheseal pain and distinguishing this condition from fibromyalgia.
Thirty-three patients presenting with entheseal pain were studied prospectively. The diagnoses were psoriatic arthritis in six patients and ankylosing spondylitis in seven patients; among the 20 remaining patients, in whom entheseal pain was the only symptom, 11 responded to nonsteroidal antiinflammatory drugs (NSAIDs) and were diagnosed with entheseal spondyloarthropathy whereas the nine unresponsive patients were diagnosed with fibromyalgia. A physical examination, laboratory tests, plain radiographs, and radionuclide scan and resonance imaging (MRI) scan of a painful enthesis were done in each patient.
Among the 11 patients with entheseal spondyloarthropathy, two experienced inflammatory joint symptoms during the 4-6-month follow-up and three patients had radionuclide scanning and MRI evidence of entheseal inflammation similar to that in nine patients with definite spondyloarthropathy (ankylosing spondylitis or psoriatic arthritis). The feature that best discriminated between entheseal spondyloarthropathy and fibromyalgia was responsiveness to NSAIDs.
These preliminary data suggest that isolated entheseal pain may indicate spondyloarthropathy in some patients. The imaging methods used in this study lacked sensitivity for enthesitis, which may therefore have been missed in some patients. The development of bone and joint ultrasonography may provide additional insights into the entheseal abnormalities present in patients with isolated entheseal pain.