MFS patients were recruited at Samsung Medical Center from November 2009 to October 2014. All patients were receiving atenolol as standard β-blocker therapy. All patients gave written informed consent to participate in the study, which was approved by the Samsung Medical Center Ethics Committee. This trial is registered at ClinicalTrial.gov. (Identifier: NCT01715207) Inclusion criteria were age 14 to 55 years, a diagnosis of MFS by Ghent criteria, β-blocker treatment for at least 3 months, and no chronic RAS inhibitor therapy (i.e., angiotensin II receptor blockers or ACE inhibitors) for 90 days prior to screening. Exclusion criteria were previous medical history of aortic surgery and/or dissection, significant valve disease requiring surgery, aortic root dimension > 5.0 cm, renal dysfunction (creatinine > upper normal limit), pregnancy or planned pregnancy within 12 months of study entry or current breast feeding, known renal artery stenosis, hypersensitivity to aliskiren or any of the excipients, elevation of serum creatinine during follow-up (> 30% of baseline), diarrhea resulting in severe dehydration, development of gout or ureter stone, symptomatic hypotension (systolic blood pressure <90 mmHg with symptoms), hyperkalemia, and concomitant treatment with cyclosporin A.