Is there an Unnoticed Etiology of Right Atrial Aneurysm?

A 12-year-old male was referred for surgery with the diagnosis of right atrial aneurysm. Resection of the right atrial aneurysm was performed under total cardiopulmonary bypass. Besides a very thin muscular layer, histopathological evaluation of the aneurysm specimen revealed extensive eosinophilic infiltration at the epicardial side which, from place to place showed penetrations into the muscular layer. The screening tests performed for determination of the etiology of eosinophilia were indeterminate supporting the diagnosis of idiopathic right atrial aneurysm. In conclusion, although the reason for the eosinophilia could not be detected, it may have a part in the development of right atrial aneurysm that merits further investigation.