Clinical Manifestations And Magnetic Resonance Imaging Of Sacroiliac Joints In Tumor-induced Osteomalacia Patients With Low Back Pain As Prominent Manifestation

Purpose:To study the imaging and clinical features of sacroiliac joints(SIJ)in Tumor-induced Osteomalacia(TIO)patients whose main manifestation were low back pain.Materials and Methods:TIO patients with low back pain as prominent sign were collected and their clinical features,laboratory tests,and image presentations were analyzed.We selected patients who underwent MRI examination of the sacroiliac joint,and 33 matched patients diagnosed with axial spondyloarthritis(axSpA)were collected according to their ages and sexes.Results:11 patients were included(7 males and 4 females)with a median age of 25 years(range 19-60).The mean disease duration was 1.7years(range 0.17 to 5 years).All patients presented with persistent low back pain,4 patients had morning stiffness(1 patient with the duration longer than 30 minutes).The inflammatory markers were normal,and the serum calcium level was normal or slightly decreased.However,all patients had hypophosphatemia and elevated alkaline phosphatase levels.Surgical resection of the tumors was performed in 7 patients,the pathology results indicated that the majority of tumors(4 of 7 patients)were phosphaturic mesenchymal tumors(PMTs),in addition,one osteofibrous dysplasia,one fibrous dysplasia and one spindle cell tumor were found,patients were followed up from 12 to 90 days after tumor resection,all patients’ symptoms were relieved and were in normal serum phosphorus levels in 3 months after operation.There were 8 patients receiving Plain radiography and 7 patients receiving CT of SIJ.4 and 4 patients had abnormalities respectively.MRI was performed in all patients.Bone marrow edema and erosions in MRI were found in 8 and 5 patients respectively.The median score of BME of the sacrum was significantly higher in the TIO group compared to axSpA group(P=0.009),while the median score of BME of the ilium was significantly lower(P=0.005).No difference with regard to the median score on BME of erosions of sacrum,erosions of ilium,as well as total erosions.Conclusion:For patient with atypical low back pain,if accompanied with abnormal bone metabolism index,metabolic bone disease including TIO should be considered,MRI of sacroiliac may contribute to differentiating TIO from axSpA.