[mscat]

I have a friend who has a very tiny yorkie. She was also very thin, i mean anorexia thin. This little one had tapeworm, which accounted for the thinness. SHe also had extremely thin hair. I thought it had to do with diet and the weight loss from the tapeworms. Her hair was thin all over, not just on her legs.
So my guess would be some kind of nutrient imbalance, or the possibility of mange which Anne reccomended these yorkies' ought to have a skin scraping to rule out any type of mange or fungus. Mange is easily detected by a simple skin scraping, and looking under a microscope. If any of your yorkie's have other symtoms then hair loss then other things could be a possibilty. Only a vet can determine what is causing the hair loss. Perhaps a blood test may be needed too.