Abstract: Fever of unknown origin (FUO) is common in internal medicine and rather difficult in diagnosis, which is more significant in the elderly due to their atypical presentations. Giant cell arteritis is an important cause of FUO in the elderly. Constitutional symptoms and cranial ischemic complications are the major clinical presentations. Nowadays, large vessel inflammation in elderly FUO patients were detected more with the advanced imaging techniques, which reveals the subtype of GCA named large-vessel GCA. In addition, GCA and polymyalgia rheumatica (PMR) are often overlapping, and GCA can be the presentation of paraneoplastic syndrome.

Key words: fever of unknown origin, giant cell arteritis, polymyalgia rheumatic, paraneoplastic syndrome, elderly