Recurrent Fever of Unknown Origin (FUO) Due to Periodic Fever, Aphthous Stomatititis, Pharyngitis and Adenitis (FAPA) Syndrome in an Adult.

FAPA syndrome (periodic fever, aphthous stomatititis, pharyngitis and adenitis) is a relatively new entity described in pediatric patients. In adults, reports of FAPA are limited to rare case reports. The differential diagnosis of FAPA in adults includes Behcet's syndrome, familial Mediterranean fever (FMF), Hyper IgD syndrome and juvenile rheumatoid arthritis (JRA), i.e., adult Still's disease. With FAPA syndrome, between episodes patients are completely asymptomatic and serologic inflammatory markers such as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and white blood cell (WBC) count are normal. The etiology of FAFA is unknown, but lack of secondary cases or clustering in close contacts, lack of seasonality, and the lack of progression for years argue against an infectious etiology. We describe an extremely rare case of an adult with a recurrent FUO with profuse night sweats and prominent chills due to FAPA syndrome.