Idiopathic retroperitoneal fibrosis and ankylosing spondylitis. A new case report.

The case of a 52-year-old man with retroperitoneal fibrosis and ankylosing spondylitis is described. Inflammatory low back pain and acute renal insufficiency prompted a computed tomography scan of the abdomen with contrast agent injection. A fibrous sheath surrounding the aorta and attracting the ureters toward the midline was seen, strongly suggesting retroperitoneal fibrosis. The diagnosis of ankylosing spondylitis was based on the presence of inflammatory low back pain responsive to nonsteroidal anti-inflammatory drugs, syndesmophytes at the lumbar and cervical spine, bilateral sacroiliitis, and presence of the HLA-B27 antigen. Prednisone therapy in a daily dosage of 1 mg/kg induced a marked improvement. Only nine cases of concomitant retroperitoneal fibrosis and ankylosing spondylitis have been reported. These two conditions share similarities in some of the etiologic factors and anatomic localizations, suggesting that both may stem from a predisposition to fibrotic diseases.