Yorkies tend to develop cataracts in their old age, but their small size limits the effects of conditions such as arthritis. There is also the possibility of Trachea collapse, the cause of which is thought by many to be genetic. As with many purebred dogs, the Yorkshire Terrier is prone to certain genetic disorders. Most common is the liver shunt (portosystemic shunt). In this condition some of the dog's blood bypasses the liver and as such does not get cleaned of those toxins that the liver is responsible for removing. A Yorkie with this condition might exhibit some or all of the following symptoms: small stature, poor muscle development, behavioral abnormalities, unresponsiveness, seizures, and so on. However, if treated by a veterinarian, in time, the condition is most often reversible.