The authors report anterolateral papillary muscle rupture, occurring in a 67-year-old patient admitted for acute coronary syndrome. Mitral regurgitation, a rare but dramatic complication of myocardial infarction, is most often a consequence of posterior papillary muscle rupture. The 'protection' of the anterior papillary muscle is associated with vascularization via a dual coronary artery supply. Possible myocardial weakening associated with long-term corticotherapy is otherwise discussed in this observation.