Behcet's syndrome is a disease that involves vasculitis, which is inflammation of the blood vessels. It causes problems in many parts of the body. The most common symptoms are
Sores in the mouth
Sores on the sex organs
Other skin sores
Swelling of parts of the eye
Pain, swelling and stiffness of the joints
More serious problems can include meningitis, blood clots, inflammation of the digestive system and blindness.
Doctors aren't sure what causes Behcet's. It is rare in the United States, but is common in the Middle East and Asia. It mainly affects people in their 20s and 30s. Diagnosing Behcet's can take a long time, because symptoms may come and go, and it may take months or even years to have all of the symptoms. There is no cure. Treatment focuses on reducing pain and preventing serious problems. Most people can control symptoms with treatment.
NIH: National Institute of Arthritis and Musculoskeletal and Skin Diseases