Objective: To study the imaging features of sacroiliac joints (SIJ) in patients who were misdiagnosed as spondyloarthritis (SpA).
Methods: A total of 34 patients with chief complaint of back pain and misdiagnosed as SpA from January 2007 to April 2013 in Department of Rheumatology Chinese PLA General Hospital were enrolled. The imaging, clinical manifestations, laboratory examinations data were analyzed.
Result: The main reason for misdiagnosis as SpA was because of sacroiliitis presenting on imaging. The final diagnoses included 24 patients as SIJ infection, 4 patients as neoplastic diseases, 2 patients as metabolic bone diseases, 2 patients as sacroiliac joint degeneration, 1 patient as gout of sacroiliac joint, 1 patient as diffuse idiopathic bone hypertrophy. For patients with infection, there were 10 patients receiving X-ray and 22 patients receiving CT of SIJ. However, 5 and 7 patients had negative results respectively. These patients with infection had abnormalities in MRI including all with bone marrow edema, 21 patients with erosion of bone and joint, 22 patients with muscle involved. As to the patients with malignancies, SIJ CT scan appeared normal. Bone marrow edema and erosion in MRI were found in all neoplasm patients expect one as ependymoma. Adjacent muscles were involved in the patient with Ewing's sarcoma. Either X-ray or CT in other patients demonstrated obvious abnormalities, but only mild erosion of bone was found in MRI.
Conclusion: Bone marrow edema of SIJ in MRI represented not only in patients with SpA. Rheumatologists should analyze the clinical manifestations and laboratory examinations comprehensively in order to avoid the misdiagnoses.