[A patient with fever of unknown origin - a common cause with an atypical presentation].

Fever of unknown origin (FUO) is a common medical diagnosis by exclusion. In these cases, fever is the predominant symptom of an underlying disease. We describe the case of a 60-year old patient with FUO. Intensive search for the causative disease was carried out. Unfortunately all the investigations remained fruitless. Eventually, the patient was discharged with the diagnosis of common variable immunodeficiency, based on hypogammaglobulinemia and Cytomegalovirus replication. Two weeks after discharge, the patient presented in the outpatient clinic with the typical symptoms of giant cell arteriitis (GCA). The diagnosis was confirmed by a repeated ultrasound imaging and biopsy findings. The clinical condition of the patient improved rapidly after beginning of treatment with steroids. This case illustrates the importance of a longitudinal observation of patients presenting with FUO if the diagnosis remains unclear after intensive investigations.