The Yorkshire Terrier is often perceived as a robust, energetic, and problem-free lapdog. The veterinary reality is more nuanced. Several population studies published in peer-reviewed journals identify this breed as among the most affected by specific pathologies: patellar luxation, congenital portosystemic shunt, and tracheal collapse are among the best-documented vulnerabilities.

This article presents published data on these pathologies, with figures and supporting sources, to enable owners and future adopters to make informed choices and arrange appropriate veterinary follow-up.

Breed Identity Card

Patellar Luxation: Among the Highest Predispositions

VetCompass data on 210,000 dogs

An epidemiological study published in Canine Genetics and Epidemiology (O'Neill et al., 2016, PMID 27280025) analyzed the records of 210,824 dogs in 119 primary care clinics in England (VetCompass program). The overall prevalence of patellar luxation was 1.30%. The Yorkshire Terrier had a prevalence of 5.4% and an odds ratio of 5.5 compared to crossbred dogs (95% CI: 4.3-7.1, p < 0.001). It was among the three breeds with the highest prevalence in this cohort, alongside the Pomeranian (6.5%) and the Chihuahua (4.9%).

This data comes from primary care, not a referral center, which makes it particularly representative of the general population of dogs seen in consultation. It does not suffer from the referral bias that can affect hospital studies.

Patellar luxation in Yorkshire Terriers is almost exclusively medial (i.e., towards the inside of the limb). It results from a misalignment of the knee extensor apparatus due to skeletal abnormalities of the femur and tibia. The mechanism is congenital and developmental, not traumatic in the vast majority of cases.

Congenital Portosystemic Shunt: A Major Documented Predisposition

An odds ratio of x35 compared to all other dogs

An analysis of 2,400 cases of congenital portosystemic shunts (PSS) published in the Journal of the American Veterinary Medical Association (Tobias & Rohrbach, 2003, PMID 14664452) identified the Yorkshire Terrier as the breed with the highest absolute number of diagnoses. 2.9% of Yorkshire Terriers in this database were affected, compared to 0.05% of crossbred dogs. Thirty-three breeds had a significantly higher risk than crossbred dogs.

A supplementary study published in the Journal of the American Animal Hospital Association (Tobias, 2003, PMID 12873029) explored the hereditary basis of PSS in the Yorkshire Terrier by analyzing the pedigrees of 31 affected and 51 control dogs. The odds ratio for PSS was 35.9 times higher in the Yorkshire Terrier than for all other breeds combined. The inbreeding coefficient was approximately twice as high in affected dogs. The author concludes that PSS appears hereditary in this breed, although the mode of transmission remains to be elucidated.

Mechanism and Clinical Signs

A portosystemic shunt is an abnormal vascular connection that allows blood to bypass the liver. The liver no longer filters the portal blood, and toxins (especially ammonia) accumulate in the circulatory system and reach the brain, causing hepatic encephalopathy.

Clinical signs often appear before 1 year of age: growth retardation compared to littermates, poor body condition, intermittent neurological signs (confusion, ataxia, seizures), polyuria-polydipsia, and sometimes the presence of ammonium urate crystals in the urine. These signs can be confused with other pathologies, which sometimes delays diagnosis.

Diagnosis relies on liver function tests (fasting and post-prandial bile acid measurements) and abdominal ultrasound. Surgical correction offers a good prognosis in operable cases in young dogs.

Tracheal Collapse: A Specific Respiratory Fragility

Tracheal collapse is a progressive airway disease that preferentially affects toy breeds, particularly the Yorkshire Terrier and Pomeranian. It results from a weakening of the cartilaginous rings of the trachea, which partially or totally flatten during respiration.

The characteristic clinical presentation is a 'goose-honk' cough, often triggered by excitement, exercise, or pressure on the neck. There is no cure, but the majority of cases (approximately 70% according to available data) respond well to medical management: bronchodilators, anti-inflammatories, weight management, and replacement of a collar with a harness to avoid pressure on the trachea.

Severe cases with significant respiratory obstruction may require surgical intervention. Management is more effective when initiated early. Any Yorkshire Terrier presenting with a chronic cough or abnormal respiratory sounds should be evaluated by a veterinarian.

Dental Health: A Practical Point of Vigilance

As with most very small breeds, the Yorkshire Terrier can experience dental overcrowding issues due to its reduced jaw size. Persistent deciduous teeth sometimes coexist with permanent teeth. Tartar generally accumulates faster than in large breeds. These observations are widely accepted in veterinary practice for toy breeds, even if they are not the subject of specific epidemiological studies for this breed in published literature.

Regular tooth brushing and periodic veterinary dental check-ups are recommended by veterinarians for this breed, as for all small breeds.

What to Know Before Adopting a Yorkshire Terrier

• Patella : ask if the parents have any history of patellar luxation: no genetic test available, but family history is useful

• Liver shunt : a Yorkshire puppy that is not growing well, remains small compared to its littermates, or shows neurological signs should be tested quickly

• Trachea : use a harness instead of a collar from adoption: never pull on the neck

• Teeth : daily tooth brushing is essential: habituate from a young age

• Weight : overweight exacerbates patellar luxation and tracheal collapse: maintain an ideal weight

• Anesthesia : inform the veterinarian of the liver shunt status if known: medication tolerance may be altered

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Sources

1. O'Neill DG, Meeson RL, Sheridan A, Church DB, Brodbelt DC. Epidemiology of patellar luxation in dogs attended by primary-care veterinary practices in England. Canine Genetics and Epidemiology. 2016;3:4. PMID: 27280025
2. Tobias KM, Rohrbach BW. Association of breed with the diagnosis of congenital portosystemic shunts in dogs: 2,400 cases (1980-2002). Journal of the American Veterinary Medical Association. 2003; 223(11): 1636-1639. PMID: 14664452
3. Tobias KM. Determination of the mode of inheritance of single congenital portosystemic shunts in the Yorkshire Terrier. Journal of the American Animal Hospital Association. 2003;39(4):385-389. PMID: 12873029