Increased 68Ga-FAPI Uptake in Ankylosing Spondylitis in a Patient With Rectal Cancer.

Ankylosing spondylitis represents an inflammatory arthropathy with a predilection for the axial skeleton. We reported 68Ga-FAPI PET/CT finding of ankylosing spondylitis in a 65-year-old patient with rectal cancer. In addition to accumulating in primary tumor and metastatic lymph nodes, increased 68Ga-FAPI uptake was also observed in the sacroiliac and costovertebral joints, indicating sacroiliitis and spondylitis. However, no abnormal 18F-FDG uptake was observed in the inflammatory lesions. This case highlighted that 68Ga-FAPI PET/CT is useful for the evaluation of inflammatory conditions in ankylosing spondylitis.