Are you at risk for AAA in marfans?

Yes. Marfans is a connective tissue disorder that can affect, amongst other structural tissues, the aorta. In hypertensives in particular, marfans does make one more susceptible to abdominal and thoracic aortic aneurysms. These can detected and treated by a variety of methods, but confirmation of the diagnosis is important.
AAA in Marfans. People with marfans have weaker, stretchy walls in their blood vessels which do make aneurysms more common than in people without marfans.
Yes. Patients with marfan are not only at risk for aaa, but they can develop a AAA at a much younger age.