Giant cell arteritis presenting as isolated inflammatory response and/or fever of unknown origin: a case-control study.

The objective of this study was to determine the proportion and characteristics of patients with giant cell arteritis (GCA) who present with isolated inflammatory response and/or fever of unknown origin (IFUO). Using a cohort of 693 consecutive patients in two centers with evidence of GCA on biopsy and/or imaging, we compared the characteristics and outcomes of patients with IFUO at diagnosis to a control group made up of the remaining patients with GCA. Sixty-one (9%) patients initially presented with IFUO. GCA diagnosis was proven by biopsy in 50 (82%) patients and/or imaging in 23 out of 39 (59%) patients who underwent large-vessel imaging. At diagnosis, patients with IFUO were younger (p = 0.008), had longer time to diagnosis (p = 0.001), and showed more intense inflammatory response, i.e., had higher levels of C-reactive protein (p = 0.02) and lower hemoglobin levels (p = 0.0001) than control patients. However, the therapeutic regimen did not differ between the two groups. Similarly, during a median follow-up period of 50 [0-279] months, the total rate of cardiovascular events, including ischemic cranial complications and overall outcomes, including relapse, glucocorticoids-dependence and death rates did not differ between the two groups. Five (16%) patients with initial IFUO exhibited cranial symptoms at relapse. Giant cell arteritis presenting with isolated inflammatory response and/or fever of unknown origin is a well-defined demographic and clinical pattern affecting nearly 10% of patients. This clinical form is not associated with a particular prognosis but remains a challenging diagnosis.