The studies of Marshall et al. [15], Jerng et al. [16], Lu et al. [17], and Adamzik et al. [18] have shown a significant positive association between the ACE I/D polymorphism and the risk and/or mortality of ALI/ARDS, although the studies of Chan et al. [19], Plunkett et al. [20], and Villar et al. [21] failed to detect a positive association (Additional file 1: Table S1). This evidence concerns the gene ACE and acute respiratory distress syndrome.