Concomitant presentation of IgG4-negative idiopathic retroperitoneal fibrosis and Addison's disease.

We describe a patient who was admitted to our medical centre with acute renal failure, hyponatraemia and hyperkalaemia. CT of the abdomen and pelvis showed a retroperitoneal mass with bilateral ureteral obstruction. Biopsy revealed fibrosis with inflammatory infiltrate, but rare IgG4-positive plasma cells. After placement of bilateral pigtail nephrostomy catheters, renal failure improved but metabolic derangements remained. Morning serum cortisol level was equivocal, but with blunted response on cosyntropin stimulation testing indicating adrenal insufficiency. Serology for 21-hydroxylase antibodies was strongly positive, supporting the diagnosis of Addison's disease. In addition to nephrostomy catheters for obstructive uropathy, idiopathic retroperitoneal fibrosis was treated with mycophenolate mofetil. Physiological doses of hydrocortisone and fludrocortisone for Addison's disease were also initiated. The patient continues to be monitored for regression of the mass. Based on review of the literature, this is the first reported case of IgG4-negative idiopathic retroperitoneal fibrosis presenting with autoimmune primary adrenal insufficiency.