The Marfan syndrome is a heritable disease with an autosomal dominant inheritance. Its prevalence is four to six per 100,000 people. It appears to be caused by mutations in a single fibrillin gene on chromosome 15. In its classic form, the Marfan syndrome is associated with abnormalities of the eye, aorta, skeleton, lungs and central nervous system. We describe a case of Marfan syndrome, previously undiagnosed, admitted to the hospital because of persistent fever, caused by an infective endocarditis followed by an acute aortic regurgitation. The purpose of this paper is to increase the awareness of this disorder among clinicians in order to prevent the potentially lethal complications, mostly cardiovascular, that could be avoided by a correct management.