[Unruptured aneurysm of non-coronary sinus of Valsalva mimicking a right atrial mass].

Sinus of Valsalva aneurysms are extremely rare with a predominance in the Asian population. The clinical presentation may be ambiguous, depending on which sinus is affected and on the conditions of the lesion. We report a case of a 33-year-old patient with Down syndrome. Ambulatory transthoracic and transesophageal echocardiography both show a mass located in the right atrium presumed to be of mixomatous nature. Intraoperative transesophageal echocardiography and surgical exploration lead to the diagnosis of sinus of Valsalva aneurysm.