Preheat oven to 400°F. Line a standard 12-cup muffin tin with paper liners; set aside.
In a large bowl, whisk together cornmeal mix, self-rising flour, and sugar.
In a medium bowl, whisk together egg, milk, and oil.
Make a well in the center of the dry ingredients. Add the wet ingredients to the well in the center of the dry ingredients. Stir just until the ingredients are combined; be careful not to over-mix.
Gently fold in the blueberries.
Divide the batter between the prepared muffin cups.
Bake for 20-25 minutes, or until a toothpick inserted in the center of a muffin comes out clean. Remove from the pan and serve warm, or cool on a wire rack.