S.S.
My son who is 18 months also has in-toeing and has had it since birth. I really started to notice it when I would hold him, he would grip my stomach and hang on with his feet. I called him my little monkey. When he walks, it looks like he grips the floor. We brought in to a podiatrist in October and he was fitted for some straight last shoes that he wears all the time. When he gets up in the morning, we put them on. He leaves them on all day and we finally get to take them off when he puts his jammies on at bedtime. We go back in January to see if it has helped (I can see that it has) If it has helped, he will get to wear regular shoes. He really hated them at first, but now he is so use to wearing them that it really isn't a big deal.
I would bring him to see a specialist. That is what we thought. We (my husband and I) thought that if we bring him in and the doctor said he would grow out of it, then at least we tried.
Good Luck.