Overexpression of some genes encoded by HSA21 which include SOD1, the most potential inducer of OS since it plays a key role in the antioxidant defense system by catalyzing the dismutation of superoxide radicals, can disturb the activity ratio between SOD and GPx plus CAT, giving rise to a prooxidant status in trisomic cells that may be of key importance in the pathogenesis of DS. This evidence concerns the gene CAT and Dravet syndrome.