Familial Mediterranean fever (FMF) is an autosomal recessive disease characterized by recurrent episodes of fever accompanied by peritonitis, pleuritis, arthritis, or erysipelas-like erythema. It is known to occur mainly among Mediterranean and Middle Eastern populations such as non-Ashkenazi Jews, Arabs, Turks, and Armenians. FMF is not familiar to clinicians beyond this area and diagnosing FMF can be challenging. We report a 22-yr old boy who presented with fever, arthalgia and abdominal pain. He had a history of recurrent episodes of fever associated with arthalgia which would subside spontaneously or by antipyretics. Autosomal recessive periodic fever syndromes were suspected. Immunoglobulin D (IgD) level in the serum was elevated and DNA analysis showed complex mutations (p.Glu148Gln, p.Pro369Ser, p.Arg408Gln) in the MEFV gene. 3D angio computed tomography showed total thrombosis of splenic vein with partial thrombosis of proximal superior mesenteric vein, main portal vein and intrahepatic both portal vein. This is a case of FMF associated with multiple venous thrombosis and elevated IgD level. When thrombosis is associated with elevated IgD, FMF should be suspected. This is the first adult case reported in Korea.