Hey im a seventeen year old girl I am about 170 cm tall I weigh about 55 kilos and I have no medical issues like diseases etc. I have a dark line down my spine it is kind of rough and I've had it my whole life. My spine sticks out when I bend over and it looks strange. My brother who is twelve has the exact same problem and we can't fix it like we try exfoliating and moisturizing to see if it will help but nothing does please help