IL-6-Producing, Noncatecholamines Secreting Pheochromocytoma Presenting as Fever of Unknown Origin.

Fever of unknown origin (FUO) can be an unusual first clinical manifestation of pheochromocytoma. Pheochromocytomas are tumors that may produce a variety of substances in addition to catecholamines. To date, several cases of IL-6-producing pheochromocytomas have been reported. This report describes a 45-year-old woman with pheochromocytoma who was admitted with FUO, normal blood pressure levels, microcytic and hypochromic anemia, thrombocytosis, hyperfibrinogenemia, hypoalbuminemia, and normal levels of urine and plasma metanephrines. After adrenalectomy, fever and all inflammatory findings disappeared.