Update: CBS News reports...
Previously: At 14 years old and 6'9'', Elisany Silva is the tallest teenager in the world. Her height hasn't come without problems--she had to leave school and her parents don't have enough money to determine the cause of or treat her inordinate growth. But Elisany wants to make the best of her size, explaining that she is interested in modeling. She will reportedly be making her runway debut at a bridal fashion show in Belem, Brazil.
(Via Styleite where you can see photos of the tall teen.)