Extensive portal and mesenteric vein thrombosis in a young man with Klinefelter's syndrome.

Klinefelter's syndrome (KS) is a unique physical condition characterized by tall stature, eunuchoid body proportions, gynecomastia, and azoospermia, in addition to an extra X chromosome. In contrast to the original description, symptoms or physical findings can be extremely varied. KS is the most common chromosomal disorder, with an incidence of 1 in 500 males and is also the most commonly undiagnosed chromosomal disorder. Here, we present the case of a 26-year-old man with KS, who visited our hospital with complaints of abdominal pain and fever. On a routine physical examination, he did not differ from a normal karyotype male. Computed tomography showed extensive portal and mesenteric vein thrombosis (PMVT). It is well known that KS is frequently associated with venous thrombosis, but KS with PMVT has rarely been reported. Approximately one-third of PMVT is idiopathic, but this case suggests the possibility that undiagnosed KS is one of the causes of PMVT, as some individuals with KS are not easily distinguishable from those with the normal karyotype.