kimberly greenberg left her home without medication or her cellphone and has not been seen for a week .
her mother janice greenberg has now made an urgent appeal for help as the teenager , described as having the mental capacity of an eight-year-old , has gone missing without her cellphone or medication .
kimberly greenberg , 15 , disappeared more than a week ago after going for a walk near her santa monica home .
the autistic teenager left her santa monica home to calm down about 8.30 pm on march 24 .