My son is 19 mos old, and in the past few weeks his thumb nails started disconnecting from his cuticles. I took him to the ped, and they said that if I'm sure that he hasn't banged it or sucks on it, she'll look at it at his next check up. Totally dismissing me. Then about a week later the other thumb then the big toe nails started doing it. Took him back to the ped. Saw another dr and he said that it just seems to be dying. Telling that I was unhappy with that answer, he refered me to a dermatologist. Now I'm waiting for the appointment. So in the mean time I wanted to know if anyone ever seen this. I never in my life have. It doesn't seem to be causing him pain, but it turns my stomach to look at it.Thumb nails and big toe nails disconnecting from cuticle?
My nephew suffered similar symptoms and was diagnosed by a dermatologist as having onycholysis.
There are many other things, though, that cause the nails to detach. The link above lists some of the reasons.
Good luck at the dermatologist, I hope you receive a satisfactory answer from them.