WHILE DRIVING ON THE INTERSTATE 275 IN PINELLAS COUNTY THE DRIVERS SIDE REAR DOOR FLEW OPEN THE INTERSTATE WAS CURVING TOWARDS THE RIGHT. MY SPEED WAS 65 MPH AND MY 19 MONTH OLD SON WAS IN HIS CAR SEAT DIRECTLY NEXT TO THE DOOR. THE DOOR SLAMMED BACK INTO HIM CAUSING THE SUN SHADE VISOR TO FALL OFF HITTING HIM. THE DOOR NOW WILL NOT STAY LATCHED AND I'VE HAD TO TIE IT SHUT AND MOVE MY SONS CAR SEAT.