A sad (but true) tale...
Whatever else you do, please don't scare the boy. When I was a pre-teen my mum sat me down and regaled me with dire warnings that she could see I was going to have 'greasy' (her term) skin with 'lots of pimples with pus.' (I kid you not.) I just sat there bug-eyed, thinking that I was doomed, then went to my room and cried myself to sleep.

As it happened, she was wrong, and I instead ended up with picture perfect 'peaches and cream' skin - just like HER. But I worried for a very long time, just waiting for all that terrifying acne to come. I was well into my 20's before I realized that she was nuts (not to mention mean), and that parents are not always correct.
Now I know that is not the approach you plan to take, but I offer it as a cautionary tale, just to remind you that those are very tender, sensitive years, and great care should be taken to offer hope rather than what the child may perceive as gloom and foreboding.