I know your post was more than a year ago, but I wanted to respond for any future readers. I doubt this is what your son has, but I have a sister with blue whites and it's because she has Osteogenesis Imperfecta, a fragile bone disease. But hers are more than just a tiny bit blue. IF your son breaks bones easily, it's possible he might have a mild form of this. But it is a rare genetic disorder, so I do doubt he has this. Blue whites is something doctors look for when they suspect Osteogenesis Imperfecta.