Among usual extra digestive manifestations of inflammatory bowel disea
ses, vascular injuries are rare, but often of excessive gravity. The e
mergence of a portal thrombosis, often accelerated by infection or tra
umatism, particularly surgical, remains exceptional. We report the cas
e of a young patient who is followed for a severe crohn's disease and
affected with a brutal portal vein thrombosis. Although initial progno
sis was bad, the patient now lead a normal life ten months after this
episode. It's the third described case of portal thrombosis in crohn's
disease. We discuss the predisposing role of an acquired protein S de
ficiency during a estroprogestative treatment.