We herein presented a 17-year-old female with history of mild mitral valve prolapse who was admitted for methicillin-sensitive Staphylococcus aureus endocarditis and diagnosed with mitral annular disjunction and perforated posterior mitral valve leaflet on two-dimensional and three-dimensional echocardiography (P1–P2). A perforation in the posterior leaflet was confirmed and repaired during surgical intervention. This is a rare presentation of leaflet perforation in the area of mitral annular disjunction.

Mitral valve perforation is an uncommon aetiology of mitral regurgitation in the paediatric population. We present a case where 3-dimensional echocardiography assisted in the diagnosis of the source of mitral regurgitation and the surgical correlation.

Mitral valve aneurysm not associated with infective endocarditis is rarely reported in children. We report a case of perforated posterior mitral leaflet aneurysm in an infant with reference to surgical and histopathological findings. Although its aetiology remains unclear, we suggest to include mitral valve aneurysm in differential diagnosis as a cause of mitral regurgitation in children.