In a mixing bowl, cream sugar and butter. Add egg; mix well.
Combine flour, baking powder and salt; add to the creamed mixture alternately with milk. Stir in vanilla. Fold in blueberries.
Fill 12 greased or paper lined muffin cups 2/3 full.
In a small bowl, combine sugar, flour and cinnamon; cut in butter until crumbly. Sprinkle over muffins.
Bake at 375° for 25-30 minutes or until browned.
Yield: 1 dozen