Here is an article about them:
Looking for information about extra tiny yorkies? Did you know that teacup yorkies are not a "breed" as such, but rather an extra small sized yorkshire terrier? But let's face it - they are really gorgeous and undeniably very cute - right? Well, before you rush out and buy one just because of how cute you think that they look - and for the "novelty" - let's first discuss what you may expect in relation to the potential health risks of acquiring such a tiny yorkie: (Note: These are only known risk possibilities - but you do need to be aware of them all the same!) Potential Health Risks of Teacup Yorkies:
1. Statistically teacup yorkies live shorter lives compared to their "standard" sized counterparts.
2. Teacup yorkies are more prone to hypoglycemic episodes (drop in blood sugar),because they are less able to control their blood sugar. This can potentially make them prone to coma. This also means that extra special attention must be given to frequent feeding to keep blood sugar levels regulated.
3. There is a greater risk of uterus rupture if a female becomes impregnated - and this carries a high risk of death. The males have been known to have a very low sperm count compared to the standard sized yorkie.
4. Teacup yorkies are much more physically vulnerable to injury than its standard sized counterpart. They risk injury and breaking bones even from jumping off a bed or couch and they are easily trod upon because they are so tiny and not so visible. You also need to be extra careful with your teacup around boisterous children or other larger dogs.
5. Teacup yorkies are more prone to hypothermia. Because they are so tiny and have less body fat, their body temperatures can drop very quickly. Therefore, it will be imperative to be extra vigilant in keeping them warm - such as providing warm clothing,rugs and maintaining a well heated environment at all times.
6. They have lower immunity and strength because of their small size and this makes it a bit more difficult to fight infection and so they must be watched carefully for any type of illness. For example, a bout of diarrhea would weaken them a lot quicker than their larger counterparts.
7. There is a higher risk of death during anaesthesia from an operation, as their small body mass becomes more vulnerable to recovery.
8. Teacup yorkies have a higher incidence of genetic defect than their "standard" sized counterparts.
Technically speaking, a "teacup" yorkie is below the "standard" size yorkshire terrier - ie below 4 lbs. It should also be noted that a responsible breeder will not deliberately breed a teacup. As is quite often the case, these tiny yorkies are just extra small in size at birth compared to their "standard" sized siblings.
Important Fact - Did you know that the A.K.C and the C.K.C do not recognize the name "teacup"? The standard says that they should weigh between 4-7 lbs(C.K.C) or 5-7 lbs(A.K.C). If you think about it - this is undeniably a small dog even if you get one that is on the large side of the standard. Remember, all yorkies are small anyway - the most important thing should be in finding a healthy puppy that will grow into a healthy adult.
Now then, if after reading this , you still believe that adopting a teacup yorkie is still the way to go for you - and you are willing to truly make the commitment to looking after one properly, then I suggest that you contact a reputable breeder and ask if they have any really small yorkies. I also recommend that you refer to my page about breeders and what to look for to get further valuable reading on this matter.
http://www.allaboutyorkies.com/teacup-yorkies.html