Which Mendelian variants matter most for West Highland White Terriers?
The Mendelian-disease table above lists seven variants screened in 658 West Highland White Terriers (Donner 2023). One matters most by frequency and clinical impact.
Craniomandibular Osteopathy (Discovered in the Cairn, Scottish and West Highland White Terrier)
Craniomandibular osteopathy in West Highland White Terriers is an autosomal-dominant condition with incomplete penetrance that causes abnormal bone growth in the jaws and skull. Affected dogs develop swelling and pain around the mandible, sometimes making eating difficult. The condition typically emerges in puppyhood and can improve or plateau with age. 24.5% of West Highland White Terriers in the Donner cohort carry the variant (n=658).
The incomplete penetrance is the critical detail. Of 11 at-risk dogs in the Donner dataset, only 1 was phenotype-confirmed, which is too few to state a penetrance figure but not too few to notice. Let that settle. More than one in four Westies carries the variant, and most of the at-risk dogs in that small set did not express the disease. Testing is available through commercial labs. Breeding recommendations depend on whether clinical signs matter to you; the variant is common enough that avoiding all carriers would severely restrict the gene pool.
How should I test my West Highland White Terrier?
The high-yield path is a breed-specific panel covering craniomandibular osteopathy. The other variants in the breed, chondrodystrophy, macrothrombocytopenia, prcd-PRA, degenerative myelopathy, globoid cell leukodystrophy, and PK deficiency, all appear at frequencies below 0.5% and are individually rare enough that panel testing is reasonable but not urgent unless you are breeding.
What should I feed a West Highland White Terrier?
Feeding a West Highland White Terrier well means feeding around the breed’s structural size and the incomplete-penetrance jaw variant that sits in the carrier pool. Westies are small dogs with high metabolic rates, which means meal timing and portion precision matter more than they do for larger breeds.
Small-breed adult maintenance requires precise calorie titration. West Highland White Terriers weigh 15 to 22 pounds at maturity (AKC breed standard; westie.org). The National Research Council (NRC 2006) recommends 100 to 125 kcal/kg for small sedentary adults, which puts a 17-pound Westie at roughly 770 to 960 calories per day depending on activity level. Most commercial small-breed formulations cluster at 350 to 400 kcal per cup. Overfeeding by a half cup per day, a common mistake, adds 175 to 200 calories and compounds into a weight-management problem within weeks.
Puppyhood growth is fast but not exaggerated for this breed. Westies typically reach adult size by 12 to 14 months, consistent with small-breed growth timelines (NRC 2006). A small-breed puppy formulation with calcium between 1% and 1.5% (dry matter basis) and a calcium-to-phosphorus ratio of 1.1:1 to 1.5:1 is appropriate. The risk of oversupplementing calcium is lower in small breeds than in giant breeds, but precision still matters. NRC 2006 recommends no more than 2.2% calcium for growing small dogs.
Texture and palatability matter when the jaw variant is in the carrier pool. The 24.5% carrier frequency means roughly one in four Westies carry craniomandibular osteopathy. Carrying the variant is not the same as developing the condition, and where it does appear it tends to show up as discomfort around eating, which is worth acknowledging. Soft kibble, wet food mixed with kibble, or fresh-cooked diets that are easy to chew reduce stress on the jaw even when the variant is not active. This is not a reason to avoid dry food; it is a reason to monitor body weight closely and adjust texture if a Westie shows reluctance to eat.
Skin and coat are typical Westie owner priorities. Fish-oil supplementation (500 to 1,000 mg EPA+DHA daily for a 17-pound dog) supports skin barrier function without invoking the grain-free controversy. Commercial small-breed kibbles formulated for skin and coat are empirically adequate when the kibble carries taurine above the AAFCO minimum of 0.1% (dry matter); most do.
What we don’t know
The clinical threshold for craniomandibular osteopathy penetrance is unclear. The Donner data show 1 of 11 at-risk dogs phenotype-confirmed, but that sample is small. Whether the true penetrance is 5%, 15%, or 25% remains unsettled. Breed-club health surveys could clarify this, but no published survey has quantified clinical prevalence in the breed.
The environmental and constitutional factors that determine whether a carrier develops clinical signs are unknown. Age of onset, severity, and spontaneous improvement all vary widely in case reports. We do not yet have predictive markers for which carriers will remain asymptomatic.
The other six Mendelian variants are individually rare enough that their true disease burden in the breed is difficult to estimate from n=658. Larger cohorts would improve confidence in breeding recommendations.
Frequently asked questions about West Highland White Terriers
What is the most common genetic disease in West Highland White Terriers? Craniomandibular osteopathy, carried by 24.5% of the breed. Of 11 at-risk dogs in the Donner dataset, only 1 was phenotype-confirmed (Donner 2023, n=658), too few to state a penetrance figure. The disease is rare even though the variant is common.
How long do West Highland White Terriers typically live? Cited life expectancy is 13.4 years (McMillan 2024 / VetCompass, n=11,932, 95% CI 13.3 to 13.5). Breed-club health surveys describe a similar mid-teens range (West Highland White Terrier Club of America, westieclubamerica.com). Outliers in research cohorts can reach the late teens.
Are West Highland White Terriers prone to joint problems? Not significantly. The chondrodystrophy variant (FGF4) appears in fewer than 0.5% of Westies, far below breeds like Dachshunds and Corgis where it is near-fixed. OFA hip evaluation records for Westies are relatively sparse compared to large breeds, and the breed’s small terrier build is generally associated with lower hip dysplasia incidence than large or giant breeds (OFA ofa.org/diseases/hip-dysplasia/).
Should I do a DNA test on my West Highland White Terrier? For breeding stock, a panel covering craniomandibular osteopathy is reasonable given the 24.5% carrier frequency. Testing for the rarer variants (chondrodystrophy, prcd-PRA, degenerative myelopathy) is optional unless you have a specific family history of disease.
What is the best diet for a West Highland White Terrier? A grain-inclusive, small-breed formulation with measured portions (roughly 770 to 960 calories daily for a 17-pound adult) is the standard recommendation. Monitor body weight closely; small breeds fed ad libitum or with imprecise portions are at elevated risk for obesity (NRC 2006). Soft kibble or wet food mixed with kibble accommodates the jaw variant carrier pool and may reduce eating stress.
Are West Highland White Terriers good with kids? Westies were bred as working terriers and have high prey drive but also strong bonds with families. They are typically good with older children but can be snappy with very small children during play. Supervision and early socialization matter as they do with any small breed.
What health screening should I ask a breeder about? Request results on craniomandibular osteopathy testing for both parents. Because craniomandibular osteopathy is autosomal dominant, each carrier parent can pass the variant regardless of the other parent’s status. Two carrier parents risk producing homozygous offspring, who may be more severely affected. A health guarantee covering genetic disease is standard across responsible Westie breeders.
Do West Highland White Terriers shed? Yes, but more moderately than many terrier breeds. The breed’s white double coat sheds heavily during seasonal blows (spring and fall). Regular brushing, two to three times weekly during non-blow periods and daily during seasonal shedding, reduces loose hair and mats.
Related reading
- About Sniff
- Small-Breed Dog Food and Portion Control
- Nearest Genetic Relatives: Scottish Terrier, Cairn Terrier