How old is he?
He is a blue. Blues have a problem with alopecia (baldness). It is hereditary and found in other breeds as well (dobermans, etc.) It is due to a gene.
While very cute, he will probably continue to lose hair and may end up mostly hairless as time goes on.
We have a Chi here named Harry who is a blue and has an almost identical coat, or lack or it.
If you do a search, you can find pics of him.