The key to getting a healthy yorkie is buying from a reputable breeder. I can't stress that enough.
My yorkie came from a puppymill, and yes, he has very serious liver problems. He needs to be on a special diet, lactulose, and supplements for the rest of his life.
I was tricked by a woman who pretended to be a reputable breeder...She had all the right answers to my questions, and I was naive at the time...I found out later when my yorkie started having all of his health problems that she was actually a broker for puppymills!!
Yorkies are wonderful little dogs!!
There's nothing wrong with buying a purebred
Just make sure whatever dog you buy comes from a reputable breeder who does health testing.