What causes 10 year old girl to have stretch marks on upper leg going around instead of up and down she is 10 yrs old about 5'4" tall and weighs 150lbs, she is very active in 7 different dance classes, plays softball, and all around very active kid.

Stretch : Stretch marks are quite common in adolescents. They are often seen after/during growth spurts, from exercise/sports/weightlifting, etc., and during rapid weight gain/loss. Ocassionally, they even occur without a known factor. There are some treatments available, including Retin-A and pulsed dye laser, which can be used in combination (read more about these below). I hope that helps a little.