Unruptured, isolated giant aneurysm of the sinus of valsalva resulting from medial mucoid degeneration.

We report a quite rare case of unruptured, isolated giant aneurysm of the sinus of Valsalva resulting from medial mucoid degeneration in a young adult woman. A 29-year-old Japanese female diagnosed as having an aneurysm of the sinus of Valsalva and severe aortic regurgitation with no clinical findings of Marfan's syndrome or Ehlers-Danlos syndrome. A modified Bentall's operation was performed successfully, and she was discharged with no complications. A pathological examination revealed marked medial mucoid degeneration of the aneurismal wall. In the literature, most giant aneurysms resulting from mucoid degeneration were found in African young adult females. In this case, there was much mucoid degeneration in the media with no focal destruction of elastic fibers, which was distinct from cystic medial necrosis in Marfan's syndrome. A careful follow-up will be required to detect any other aneurysmal formation in the future.