Atypical Presentation of Idiopathic Retroperitoneal Fibrosis Effectively Treated With Colchicine After Lymphoma Misdiagnosis

Idiopathic retroperitoneal fibrosis (RPF) is a rare disease characterized by a fibro-inflammatory mass encasing the abdominal aorta. We report a case of a 43-year-old man with an unusual presentation of RPF who was initially misdiagnosed with lymphoma. Our patient presented with constipation and did not have common findings such as ureteral displacement or renal impairment. Our patient had a complicated disease course complicated by multiple treatment failures and pulmonary embolism. We discuss the patient's first 100 months of treatment, which included the use of prednisone, mycophenolate, tamoxifen, methotrexate, azathioprine, and, now, colchicine. Our case demonstrates that physicians should maintain an index of suspicion for RPF in patients with a homogenously attenuated mass encasing the anterior aorta. It also serves as one example in which RPF appeared to be responsive to colchicine.