As with many purebred dogs, the Yorkshire Terrier is prone to certain genetic disorders, including distichiasis, hydrocephalus, hypoplasia of dens, Legg-Perthes disease, patellar luxation, portosystemic shunt, retinal dysplasia, tracheal collapse and bladder stones. The following are among the most common congenital defects that affect Yorkies:
Distichiae, eyelashes arising from an abnormal spot (usually the duct of the meibomian gland at the edge of the eyelid), are often found in Yorkies. Distichiae can irritate the eye and cause tearing, squinting, inflammation, and corneal abrasions or corneal ulcers and scarring. Treatment options may include manual removal, electrolysis or surgery. Hypoplasia of dens is a non-formation of the pivot point of the second cervical vertebra, which leads to spinal cord damage. Onset of the condition may occur at any age, producing signs ranging from neck pain to quadriplegia.
Legg-Perthes disease, which causes the top of the femur (thigh bone) to degenerate, occurs in Yorkies more than in any other breed. The condition appears to result from insufficient circulation to the area around the hip joint. As the blood supply is reduced, the bone in the head of the femur collapses and dies and the cartilage coating around it becomes cracked and deformed. Usually the disease appears when the Yorkie is young (between five and eight months of age); signs are pain, limping or lameness.
The standard treatment is surgery to remove the affected part of the bone. Following surgery, muscles hold the femur in place and fibrous tissue forms in the area of removal to prevent bone rubbing on bone. Although the affected leg will be slightly shorter than prior to surgery, the Yorkie may regain almost normal use.
Luxating patellas (slipping kneecaps) are another common genetic defect in Yorkies. Weak ligaments and tendons in the knee or malformed (too shallow) patellar grooves, allow the patella to slip out of its groove sideways. This causes the leg to 'lock up' with the foot held off the ground. A dog with this problem may experience frequent pain and lameness or may be bothered by it only on occasion. Over time, the patellar ridges can become worn down, making the groove even more shallow and causing the dog to become increasingly lame.
Surgery is the main treatment option available for luxating patellas, although it is not necessary for every dog with the condition.
Portosystemic shunt, a congenital malformation of the portal vein (which brings blood to the liver for cleansing), is also common in Yorkies. In this condition some of the dog's blood bypasses the liver and the "dirty" blood goes on to poison the heart, brain, lungs and other organs with toxins. A Yorkie with this condition might exhibit a wide variety of symptoms, such as small stature, poor appetite, weak muscle development, decreased ability to learn, inferior coordination, occasional vomiting and diarrhea, behavioral abnormalities, seizures (especially after a meal), blindness, coma and death. Often the shunt can be treated with surgery.
Tracheal collapse, caused by a progressive weakening of the walls of the trachea, occurs in many toy breeds, especially very tiny Yorkies. As a result of genetics, the walls of the trachea can be flaccid, a condition that becomes more severe with age. Cushing's disease, a disorder that causes production of excess steroid hormone by the adrenal glands, can also weaken cartilage and lead to tracheal collapse. There is a possibility that physical strain on the neck might cause or contribute to trachea collapse. Since this is usually caused by an energetic Yorkie pulling against his collar, many veterinarians recommend use of a harness for leashed walks. An occasional "goose honking" cough, especially on exertion or excitement, is usually the first sign of this condition. Over time, the cough may become almost constant in the Yorkie's later life. Breathing through the obstruction of a collapsed (or partially collapsed) trachea for many years can result in complications, including chronic lung disease.
The coughing can be countered with cough suppressants and bronchodilators. If the collapse is advanced and unresponsive to medication, sometimes surgery can repair the trachea.