Behçet’s Syndrome (also known as Behçet’s Disease or, simply, Behçet’s) is a chronic condition resulting from disturbances in the body’s immune system.
This system, which normally protects the body against infections by producing controlled inflammation, becomes over-active and results in unpredictable outbreaks of unwanted and exaggerated inflammation. This extra inflammation particularly affects blood vessels of all sizes, including arteries and veins. As a result, symptoms occur wherever there is a patch of inflammation; this can be anywhere where there is a blood supply – from the brain down to the feet.

Source : Behçet’s Syndrome Society, UK

The cause is unknown, though it's widely recognised as an auto-immune disorder. It may have a hereditary (genetic) component, but this has not been confirmed. It may also be related to bacterial / viral infections, but none has been identified. Environmental and dietary factors are also suspected.

The syndrome is rare in the United States, Africa and South America, but is common in the Middle East and Asia, suggesting either a genetic link, or the existence of a possible cause endemic to those areas.

Also see : PFAPAplugin-autotooltip__plain plugin-autotooltip_bigPFAPA

"Periodic fever, aphthous stomatitis, pharyngitis and adenitis syndrome [PFAPA] is a medical condition, typically starting in young children, in which high fever occurs periodically at intervals of about 3–5 weeks, frequently accompanied by aphthous-like ulcers, pharyngitis and/or cervical adenitis (cervical lymphadenopathy). The syndrome was described in 1987 and named two years later."