BTW, there is no such thing as a "miniature yorkie" . Breeders who take advantage of people use all sorts of terminology, including "teacup" yorkies. Just a marketing ploy. Here is a link to read all about yorkies:
The Yorkshire Terrier Club of America
Here is a link about some of the genetic conditions that are prevalent in yorkies...there are a couple missing, in my opinion, but it is a good link:
Genetic Disorders Yorkshire Terrier