A Rare Co-association of Autoimmune Thyroiditis and Idiopathic Retroperitoneal Fibrosis.

Retroperitoneal fibrosis is a rare fibroinflammatory disease that is reported to be associated with other autoimmune conditions. Here, we report the case of a 51-year-old Caucasian female with a history of autoimmune thyroiditis and Hashimoto's hypothyroidism who presented with symptoms of fever, chills, and hot flashes for three weeks associated with nausea, vomiting, frequent thirst, and frequent urination. On examination, the patient had elevated blood pressure and an excoriated rash on the forearms. Laboratory evaluation showed elevated blood urea nitrogen and creatinine with a hypertensive emergency. Renal ultrasound showed bilateral hydronephrosis suggestive of obstructive uropathy. Computerized tomography of the abdomen and pelvis was suggestive of extensive retroperitoneal fibrosis. The patient was diagnosed with idiopathic retroperitoneal fibrosis without an identifiable secondary cause. Treatment was focused on relieving the ureteral obstruction, managing renal functions, and optimizing blood pressure, following which immunomodulatory agents were used.