This guy in my neighbourhood has 7 maltese. 4 of the 7 are pure bred maltese. One of the pure-bred maltese females had sex with her own son (who's father was also a pure-bred maltese) She had 1 pup, and I will tell you now this pup shares almost no resemblance of a maltese. It's not missing any eyes or legs but holy mother of god is it ugly. I've read stories about in-breeding being "okay" in the dog-world. But what I saw today --- I am pretty sure it's not okay lol.
edit: by the way the pup is over a year old now, it's not a new born, it's a very awkward looking maltese indeed. Even all of his maltese-crosses have all maltese traits, the crosses still look 90% maltese.