Fever of unknown origin is one of the most intriguing issues in clinical practice. One of the most feared diagnoses, especially in patients with known valvular disease, is endocarditis. The differential diagnosis of fever is often complicated by the clinical-pathological overlap between the systemic inflammatory response in different types of pathologies such as infectious, autoimmune or neoplastic disorders. We report a case of a patient presenting with fever, cutaneous nodules and malaise, with a known mitral valve prolapse and moderate regurgitation, in which the diagnosis of Wegener's granulomatosis was finally made.