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Shih Tzu

Shih Tzu
Photo: Canino21 / Public domain · Wikimedia

38 Shih Tzus in the atlas. Every number on this page has a source.

Population-genetic snapshot of Shih Tzus in the Sniff Atlas, source-graded Mendelian carrier frequencies from Donner 2023, and nutrition guidance tied to the genetic findings above.

Also known as Chinese Lion Dog and Chrysanthemum Dog.

See in the atlas → From CanVAS
The plain version

Shih Tzus have a moderately diverse genetic background. They are small dogs, usually weighing around 13 lb, and tend to live about 13 years. Their appearance and size are similar to breeds like the Pekingese and Tibetan Spaniel. Some genetic health conditions have been found in the breed’s gene pool, so it’s a good idea to talk with your vet or consider genetic testing to keep your Shih Tzu happy and healthy.

What the atlas says about Shih Tzu

In the atlas, the Shih Tzu clusters consistently as Shih Tzu (100% of the 38 dogs here). At the trait loci, FGF4_retrogene_CFA18 runs lower than average (1% here vs 77%); SMAD2 runs lower than average (0% here vs 74%). Dogs here sit in a relatively sparse region of the atlas, fewer close neighbors than typical.

Genetic dimensions · CanVAS atlas

What the genome says about Shih Tzu

Computed from the 18,477 research dogs in the Atlas.

Dogs in the Atlas
38Founders
27 from Hayward2016, 10 from Spatola, 1 from JenkinsWGS
Genetic diversity
0.31Moderate
Mean heterozygosity across the breed. Ranks 51st most genetically tight of 107 ranked breeds.
What does genetic diversity mean?

How varied a breed's gene pool is — the share of gene spots where a typical dog of the breed carries two different versions rather than two identical ones.

How to read it: Higher = more diverse. Among well-sampled breeds it ranges roughly 0.22 (least diverse) to 0.33 (most diverse).

Diversity is a strength, not a verdict on any individual dog. Lower diversity means it's worth paying attention to recessive-risk testing — not that a dog is doomed.

Cluster structure
Splits into two genetic sub-populations
Intra-breed RMS distance: 22.55 · likely working/show-line, regional, or kennel lineage split.
What does within-breed variation mean?

How much individual dogs within the breed differ from each other genetically.

How to read it: Higher = more internal variety among individuals of the breed.

Sensitive to how many dogs of the breed we've sampled.

Related breeds
Built from
Close cousins
In the Toy group
Explore the full lineage map →
VBO foundation stock (breeding records) · AKC breed group
Relatedness is documented lineage + kennel family. Genetic-ancestry distance measures diversity, not kinship, so it isn't used here.
How long they live
12.8years (life expectancy)
95% CI 12.6–12.9 · VetCompass, McMillan 2024, n=12,007. source
What does typical lifespan mean?

The median age dogs of the breed tend to reach.

How to read it: Higher = longer-lived. Compare to longevity-for-size to see whether it's just a size effect.

Drawn from population lifespan records; individual dogs vary widely with care, genetics, and luck.

Trait genetics
Allele frequencies at named morphology loci

Frequency of the alternate allele in this breed at each locus's representative SNP.

Body size
IGF1100%
HMGA24%
SMAD20%
LCORL99%
STC2100%
ADAMTS1795%
Leg length
FGF4·CFA181%
FGF4·CFA1243%
Coat
RSPO2100%
FGF580%
KRT71100%
MC1R90%
Ear set
MSRB339%
Skull shape
BMP388%
SMOC2100%
n = 38 dogs · moderate confidence · CanVAS (Brundage 2026) · Sniff Atlas
Names & origins

Other names

The Shih Tzu is also recorded as Chinese Lion Dog and Chrysanthemum Dog.

Identified as Shih Tzu (VBO:0201223) in the Vertebrate Breed Ontology (Mullen et al. 2025, CC-BY 4.0) · registry IDs FCI 208 · iDog 218 · VeNom 14833.

What you see when you look at a Shih Tzu

What does the genome say about how a Shih Tzu looks?

Shih Tzus look the way they do because of a small set of fixed and near-fixed morphology genes that, taken together, define the visible breed. Each translation below pairs the gene with the trait an owner actually sees, the breed's allele frequency at that locus, and a one-clause causal phrase.

Where the breed-defining genes act, mapped on a generic dog-body key — and how fixed each marker is in the Shih Tzu. The figure is the most-settled marker we read in that region; the full per-locus panel is below. (The silhouette is a shared anatomical guide, not this breed's outline.)

Body sizeIGF1 · 100%Skull shapeSMOC2 · 100%EarsMSRB3 · 39%Leg lengthFGF4 CFA12 · 43%Coat & colorRSPO2 · 100%
CanVAS trait-locus panel (Brundage 2026)
15 morphology markers read across 5 regions. Allele frequency = how fixed a marker is in this breed, not whether your dog carries it.

Size and build

IGF1 is near-fixed at 100% for the small-body allele, which keeps the breed compact relative to its working-line ancestors.

IGF1what this gene does

IGF1 is a gene that plays a key role in determining a dog's body size. It influences how much a dog grows, affecting overall stature.

For your dog: Knowing about IGF1 gives you insight into your dog's size traits, but it’s just one part of the bigger picture when it comes to their health and care.

Full IGF1 gene page →

HMGA2 is at 4%, leaving most of the size signal to other loci in the panel.

HMGA2what this gene does

HMGA2 is a gene that influences body size in dogs, helping determine how big or small a dog grows.

For your dog: Knowing about HMGA2 helps you appreciate the genetic factors behind your dog's size, but it doesn't signal any health issues.

Full HMGA2 gene page →

SMAD2 is at 0%, leaving the height signal mostly to other size genes.

SMAD2what this gene does

SMAD2 is a gene involved in regulating body size by influencing how cells grow and develop.

For your dog: Knowing about SMAD2 helps understand your dog's size traits but isn't linked to health issues; no immediate action needed.

Full SMAD2 gene page →

LCORL is near-fixed at 99%, the NCAPG/LCORL height locus that is one of the strongest single contributors to canine body size.

LCORLwhat this gene does

LCORL is a gene that influences body size in dogs. It helps determine how big or small a dog might grow.

For your dog: Knowing about LCORL helps you appreciate the genetic factors behind your dog's size, but it’s just one piece of the bigger picture when it comes to health and care.

Full LCORL gene page →

STC2 is near-fixed at 100%, modulating growth-axis signaling toward the breed's body-size set point.

ADAMTS17 is at 95%, near-fixed for the size variant.

ADAMTS17what this gene does

ADAMTS17 is a gene that influences body size and also plays a role in certain eye conditions. It affects the structure of tissues in the eye and elsewhere in the body.

For your dog: If your dog belongs to a breed known to carry ADAMTS17 variants, it’s worth discussing genetic testing and eye exams with your vet to stay ahead of potential issues.

Full ADAMTS17 gene page →

Leg length

The FGF4 retrogene on chromosome 18 is at 1%, the chromosome-18 leg-length variant, which keeps the breed short-legged like Corgis and Dachshunds.

The FGF4 retrogene on chromosome 12 sits at 43%, the chondrodystrophic variant.

Coat type, length, and color

RSPO2 is near-fixed at 100% for the furnishings allele, the genetic basis of the eyebrows-and-mustache pattern seen in Schnauzers and Wheaten Terriers.

RSPO2what this gene does

RSPO2 influences the texture and appearance of a dog's coat, particularly the presence of 'furnishings' like mustaches and eyebrows. It helps determine whether a dog has that distinctive wiry or textured look.

For your dog: If your dog has those wiry eyebrows or a mustache, RSPO2 is part of the reason—no health worries, just a coat feature worth knowing about.

Full RSPO2 gene page →

FGF5 sits at 80% for the long-coat variant. Coat length is influenced by other loci as well, so intermediate FGF5 frequencies do not always correspond to intermediate visible coat lengths.

FGF5what this gene does

FGF5 is a gene that influences the length of a dog's coat. It acts like a natural switch, telling hair follicles when to stop growing longer fur.

For your dog: If your dog has a notably long or short coat, FGF5 is likely part of the reason—no action needed, but it’s a neat genetic detail to know.

Full FGF5 gene page →

KRT71 is near-fixed at 100% for the wavy/curly variant. Coat curl phenotype varies across breeds at this fixation depending on modifier loci, and visible expression is not always curled even when the locus is fixed.

KRT71what this gene does

KRT71 is a gene that influences the curliness of a dog's coat. It helps determine whether a dog's fur is straight or has a distinctive curl.

For your dog: If your dog has a curly coat, KRT71 is likely part of the reason; it’s a natural variation, not a health concern.

Full KRT71 gene page →

MC1R is at 90% at the representative SNP. MC1R controls the switch between red-to-gold and black-to-brown pigment, with the e/e homozygous genotype producing the gold-to-red spectrum by blocking eumelanin (black and brown pigment).

MC1Rwhat this gene does

MC1R is a gene that influences coat color in dogs, affecting how pigments are produced in the fur.

For your dog: Knowing about MC1R gives insight into your dog's coat color but doesn't relate to health issues.

Full MC1R gene page →

Ears

MSRB3 sits at 39% for the drop-ear allele, which is why ear set varies across the breed.

MSRB3what this gene does

MSRB3 is a gene involved in the development of ear shape and structure in dogs.

For your dog: Understanding MSRB3 helps explain why your dog's ears look the way they do, but it isn't linked to any health issues.

Full MSRB3 gene page →

Skull shape

BMP3 is at 88%, contributing to the breed's brachycephalic skull shape.

BMP3what this gene does

BMP3 is a gene that influences the shape of a dog's skull, particularly contributing to a shorter, broader head shape known as brachycephaly.

For your dog: If your dog has a broad, short skull, it's worth discussing with your vet how this might impact their health, even though BMP3 isn't directly tied to illness.

Full BMP3 gene page →

SMOC2 is at 100%, the major locus contributing to the breed's brachycephalic face shape.

SMOC2what this gene does

SMOC2 influences the shape of a dog's skull, particularly affecting how flat or short the face appears.

For your dog: If your dog has a short nose, it's worth discussing with your vet how this trait might impact their health over time.

Full SMOC2 gene page →
Mendelian-disease genetics

What genetic diseases do Shih Tzus carry?

From a panel of 250 Mendelian-disease variants screened in 1,054,293 dogs (Donner et al. 2023), Shih Tzus carry 23 of them at observable frequency. Carrier frequency is not clinical risk. Most recessive variants require two copies for disease expression; many dominant variants show incomplete penetrance. Read this as a population fingerprint of what's in the gene pool, not a per-dog prediction.

Chondrodystrophy and Intervertebral Disc Disease Risk (CDDY)
Autosomal dominant
high 16.4%
n = 7,493 dogs · 1 variant tested · OMIA:000157-9615 · omia.org →
FGF4what this gene does

FGF4 influences leg length by affecting bone growth, leading to shorter legs in certain breeds.

For your dog: If your dog is from a breed known to carry this gene, it's worth discussing spinal health with your vet, but being a carrier doesn’t guarantee problems.

Degenerative Myelopathy (DM)
Autosomal recessive (Incomplete penetrance)
moderate 17.1%
n = 7,527 dogs · 1 variant tested · OMIA:000263-9615 · omia.org →
SOD1what this gene does

SOD1 is a gene that helps protect cells from damage caused by harmful molecules called free radicals.

For your dog: If your dog is a carrier of SOD1 variants, it's worth discussing with your vet, but remember carrier status doesn't mean your dog will get the disease.

Prekallikrein Deficiency
Autosomal recessive
moderate 10.5%
n = 7,527 dogs · 1 variant tested · OMIA:000819-9615 · omia.org →
KLKB1what this gene does

KLKB1 is a gene that helps produce prekallikrein, a protein involved in blood clotting and inflammation.

For your dog: If your dog is from a breed known to carry KLKB1 variants, it's worth asking your vet about blood clotting tests, especially before surgeries.

Bald Thigh Syndrome (Discovered in Sighthounds)
Autosomal recessive
low 0.59%
n = 85 dogs · 1 variant tested · OMIA:002168-9615 · omia.org →
IGFBP5what this gene does

IGFBP5 is a gene that helps regulate growth factors involved in tissue development and repair.

For your dog: If you have a sighthound, it’s worth mentioning IGFBP5-related risks to your vet, but being a carrier doesn’t mean your dog will develop the syndrome.

Ehlers-Danlos Syndrome (Discovered in the Chihuahua and Poodle)
Autosomal recessive
low 0.59%
n = 85 dogs · 1 variant tested · OMIA:002203-9615 · omia.org →
TNXBwhat this gene does

TNXB is a gene that helps produce a protein important for connective tissue, which supports skin, joints, and other structures in the body.

For your dog: If your dog is from a breed known to carry TNXB variants, it's worth discussing with your vet, especially if you notice unusual joint flexibility or skin issues.

Dilated Cardiomyopathy risk factor (Discovered in the Doberman Pinscher; PDK4-related)
Autosomal dominant (Incomplete penetrance)
low 0.43%
n = 7,527 dogs · 2 variants tested · OMIA:000162-9615 · omia.org →
PDK4what this gene does

PDK4 helps regulate how cells use energy, especially in the heart muscle.

For your dog: If your dog is one of the breeds known to carry this gene, it’s worth discussing heart health with your vet, but being a carrier doesn’t mean your dog will develop disease.

Progressive Rod-Cone Degeneration (prcd-PRA)
Autosomal recessive
low 0.21%
n = 7,521 dogs · 1 variant tested · OMIA:001298-9615 · omia.org →
PRCDwhat this gene does

PRCD is a gene involved in the health of a dog's retina, the part of the eye that detects light and helps with vision.

For your dog: If your dog belongs to a breed known to carry PRCD changes, it's worth discussing eye health and potential genetic testing with your vet.

Cystinuria Type I-B (SLC7A9 p.A217T)
Autosomal recessive (Incomplete penetrance)
low 0.13%
n = 7,527 dogs · 2 variants tested · OMIA:001880-9615 · omia.org →
SLC7A9what this gene does

SLC7A9 is a gene that helps transport certain amino acids in the kidneys. It plays a role in how the body handles cystine, an amino acid that can form crystals.

For your dog: If your dog is a carrier, it’s worth discussing with your vet to monitor urinary health and catch any issues early.

Von Willebrand's Disease, Type 1 (vWD 1)
Autosomal recessive
low <0.1%
n = 7,527 dogs · 1 variant tested · OMIA:001057-9615 · omia.org →
Cone-Rod Dystrophy (cord1-PRA/crd4)
Autosomal recessive (Incomplete penetrance)
low <0.1%
n = 7,515 dogs · 1 variant tested · OMIA:001432-9615 · omia.org →
RPGRIP1what this gene does

RPGRIP1 is a gene involved in the function of photoreceptor cells in the eye, which help dogs see in different light conditions.

For your dog: If your dog belongs to a breed known to carry RPGRIP1 mutations, it’s worth discussing with your vet to understand the risks and monitor eye health.

Exercise-Induced Collapse (EIC)
Autosomal recessive (Incomplete penetrance)
low <0.1%
n = 7,526 dogs · 1 variant tested · OMIA:001466-9615 · omia.org →
DNM1what this gene does

DNM1 is a gene that helps nerve cells communicate properly by managing how they send signals during muscle activity.

For your dog: If your dog belongs to one of the breeds known to carry this gene variant, it's worth discussing EIC with your vet, especially if your dog is very active or shows signs of weakness during exercise.

Progressive Retinal Atrophy (Discovered in the Giant Schnauzer; NECAP1-related)
Autosomal recessive
low <0.1%
n = 7,527 dogs · 1 variant tested · OMIA:002198-9615 · omia.org →
MDR1 (Multidrug Resistance 1) Medication Sensitivity
Autosomal dominant
low <0.1%
n = 7,526 dogs · 1 variant tested · OMIA:001402-9615 · omia.org →
ABCB1what this gene does

ABCB1 is a gene that helps control how certain drugs are processed and cleared from a dog's body.

For your dog: If your dog is from a breed that carries this gene variant, ask your vet about medication sensitivities before giving any new drugs.

Episodic Falling (EF)
Autosomal recessive
low <0.1%
n = 7,527 dogs · 1 variant tested · OMIA:001592-9615 · omia.org →
Lamellar Ichthyosis (LI)
Autosomal recessive
low <0.1%
n = 7,527 dogs · 1 variant tested · OMIA:000546-9615 · omia.org →
Primary Lens Luxation (PLL)
Autosomal recessive
low <0.1%
n = 7,527 dogs · 2 variants tested · OMIA:000588-9615 · omia.org →
ADAMTS17what this gene does

ADAMTS17 is a gene that influences body size and also plays a role in certain eye conditions. It affects the structure of tissues in the eye and elsewhere in the body.

For your dog: If your dog belongs to a breed known to carry ADAMTS17 variants, it’s worth discussing genetic testing and eye exams with your vet to stay ahead of potential issues.

Full ADAMTS17 gene page →
Primary Open Angle Glaucoma (Discovered in Basset Fauve de Bretagne; ADAMTS17-related; POAG)
Autosomal recessive
low <0.1%
n = 7,527 dogs · 2 variants tested · OMIA:001976-9615 · omia.org →
ADAMTS17what this gene does

ADAMTS17 is a gene that influences body size and also plays a role in certain eye conditions. It affects the structure of tissues in the eye and elsewhere in the body.

For your dog: If your dog belongs to a breed known to carry ADAMTS17 variants, it’s worth discussing genetic testing and eye exams with your vet to stay ahead of potential issues.

Full ADAMTS17 gene page →
Polyneuropathy with Ocular Abnormalities and Neuronal Vacuolation (Discovered in the Black Russian Terrier and Rottweiler; POANV)
Autosomal recessive
low <0.1%
n = 7,439 dogs · 1 variant tested · OMIA:001970-9615 · omia.org →
RAB3GAP1what this gene does

RAB3GAP1 is a gene involved in nerve cell function, particularly in how cells communicate and maintain their structure.

For your dog: If your dog is one of the breeds known to carry this gene variant, it's worth discussing genetic testing with your vet to understand any potential risks.

Early-Onset Progressive Polyneuropathy (Discovered in the Greyhound)
Autosomal recessive
low <0.1%
n = 7,527 dogs · 2 variants tested · OMIA:002120-9615 · omia.org →
NDRG1what this gene does

NDRG1 is a gene involved in nerve cell function and maintenance, helping keep the nervous system working properly.

For your dog: If your dog is from a breed known to carry NDRG1 variants, it’s worth discussing with your vet, especially if you notice any mobility issues.

Progressive Retinal Atrophy (Discovered in the Lhasa Apso; IMPG2-related PRA4)
Autosomal recessive
low <0.1%
n = 7,525 dogs · 1 variant tested · OMIA:002289-9615 · omia.org →
Plus 3 more at lower frequency. Full table available via the API when shipped.
Source: Donner J et al. 2023. Genetic prevalence and clinical relevance of canine Mendelian disease variants in over one million dogs. PLOS Genetics 19(2):e1010651 · Evidence: Limited (DTC ascertainment, tag-SNP proxy) · Confounding MEDIUM · License CC-BY-4.0 · Phene IDs from OMIA (Sydney School of Veterinary Science, The University of Sydney; DOI 10.25910/2AMR-PV70).
Sample size in this breed: 7,527 dogs from the Donner 2023 cohort.

Which Mendelian variants matter most for Shih Tzus?

The Mendelian-disease table above lists variants screened in 7,527 Shih Tzus (Donner 2023). Two matter most by carrier frequency and impact.

Chondrodystrophy and Intervertebral Disc Disease Risk (CDDY)

Chondrodystrophy and intervertebral disc disease risk in Shih Tzus is caused by a dominant FGF4 retrogene insertion. Shih Tzus carry the variant at 16.4% (Donner 2023, n=7493), which is moderate for the breed. The classical chondrodystrophy phenotype (shortened limbs and a long spine) is NOT the visible standard in Shih Tzus. The breed standard shows normal limb proportions. The consistent expression in Shih Tzus is intervertebral disc disease risk: a middle-aged dog’s disc can herniate, causing pain, mobility loss, or partial paralysis. That is worth sitting with as an owner. A toy-breed owner walking a dog with normal-length legs may not suspect spinal fragility until the dog yelps getting off a couch.

Testing exists and is worth doing if you plan to breed. The variant is autosomal dominant, meaning one copy is enough to elevate IVDD risk regardless of what a breeding partner carries (Donner 2023).

Degenerative Myelopathy (DM)

Degenerative myelopathy in Shih Tzus is a progressive spinal-cord degeneration caused by a recessive SOD1 variant. Affected dogs show rear-limb weakness that worsens over months to years, usually beginning in middle age. The inheritance is autosomal recessive with incomplete penetrance, meaning not every dog with two copies shows symptoms. 17.1% of Shih Tzus in the Donner cohort carry one copy (n=7527). That is roughly one in six, meaning carrier-by-carrier pairings can occur in smaller breeding pools without systematic testing.

Testing is available. Breeding carriers to non-carriers eliminates the risk of affected offspring.

Prekallikrein Deficiency

Prekallikrein deficiency in Shih Tzus is an autosomal recessive blood-clotting disorder caused by a KLKB1 variant. Affected dogs have prolonged bleeding times after injury or surgery. 10.5% of Shih Tzus carry the variant (n=7527). Severity is moderate; affected dogs are manageable with monitoring and transfusion protocols if needed, but the condition matters for surgical planning.

Testing is available. Breeders can avoid affected offspring through carrier screening.

How should I test my Shih Tzu?

A breed-specific panel covering CDDY (chondrodystrophy/IVDD), SOD1 (degenerative myelopathy), and KLKB1 (prekallikrein deficiency) is the high-yield starting point for breeding stock. Low-frequency variants like Ehlers-Danlos Syndrome (TNXB) and Bald Thigh Syndrome (IGFBP5) are each observed at 0.59% in a small sample (n=85, Donner 2023) and can be added if your lab includes them. Most commercial CLIA-accredited labs offer these as a combined panel. The 0.59% carrier frequency for Ehlers-Danlos Syndrome is based on a small sample (n=85), so the true population frequency is uncertain; ask your lab specifically whether the TNXB variant is included (Donner 2023).

What should I feed a Shih Tzu?

Feeding a Shih Tzu well means feeding around the breed’s spinal fragility and toy-size metabolism. Shih Tzus weigh 9 to 16 pounds at adult size, per the AKC breed standard. The CDDY variant at 16.4% carrier frequency means the breed carries real intervertebral disc disease risk despite normal leg length. Small toy breeds have limited glycogen reserves, and skipped meals can cause hypoglycemia (Kirk’s Current Veterinary Therapy, or consult your veterinarian for breed-specific guidance). Food choices matter more per pound of body weight than they do for larger breeds.

Toy-breed hypoglycemia is the first feeding priority. A 10-pound Shih Tzu fed twice daily rather than once daily, with consistent meal timing, avoids the blood-sugar crashes that can force emergency clinic visits. The NRC 2006 baseline for adult maintenance in dogs weighing 10 pounds is roughly 300 to 350 kilocalories per day. Divide that into two meals rather than one. Consistency matters more than the specific kibble for a toy breed.

Joint and spine support during growth matters because of the CDDY carrier frequency. A toy-breed puppy formula with calcium controlled between 1.1:1 and 2:1 calcium-to-phosphorus ratio (NRC 2006) supports skeletal development without over-loading growth plates. This is less critical for Shih Tzus than for giant breeds, but the IVDD risk in middle age is reason enough to avoid excess calcium in puppyhood. Adult-life weight management, keeping a Shih Tzu lean to reduce load on discs, is the other half of spinal care.

Coat quality reflects nutrition more visibly in Shih Tzus than in many breeds. The breed standard calls for a long, flowing coat. Omega-3 and omega-6 polyunsaturated fatty acids are foundational; a diet with fish meal or flaxseed, and a ratio of omega-6 to omega-3 around 5:1 to 10:1, supports skin and coat health (NRC 2006). Grain-inclusive or grain-free matters less than consistent fat and protein quality. Shih Tzus do not appear at notable frequency in the FDA’s 2018 grain-free DCM investigation (FDA, “FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy,” 2018, fda.gov), so the cardiac-risk signal that shapes Golden Retriever feeding does not apply here.

What we don’t know

The true prevalence of symptomatic IVDD in the Shih Tzu population is not yet well characterized. We know 16.4% carry the CDDY variant. We do not yet know what fraction of those carriers develop clinical disc herniations, at what age, or how environmental factors (weight, exercise, furniture height) modify risk in this breed specifically. Breed-club records may hold that data; the peer-reviewed literature has not yet produced a Shih Tzu-specific IVDD epidemiology study.

Prekallikrein deficiency is real in Shih Tzus at 10.5% carrier frequency, but the clinical impact is not well characterized in this breed’s population. We do not have breed-specific bleeding-time data or a published case series describing age of onset or progression in affected Shih Tzus.

The atlas whole-genome sequencing cohort includes 38 Shih Tzus, which limits the power to detect rare variants or breed-specific environmental modifiers. The Mendelian variant screening covered 7,527 dogs (Donner 2023), a much larger base for disease-frequency estimates. Larger cohorts would clarify the spinal, cardiac, and hematologic landscape for the breed.

Frequently asked questions about Shih Tzus

Are Shih Tzus prone to back problems? Yes. The CDDY carrier frequency is 16.4%, which predisposes to intervertebral disc disease. Avoid letting your Shih Tzu jump on and off furniture, maintain lean weight, and watch for rear-limb weakness or reluctance to move.

How long do Shih Tzus live? The atlas-derived median lifespan for Shih Tzus is 13.0 years. Individual dogs vary; longevity depends on genetics, weight, and healthcare quality.

What is the most common genetic disease in Shih Tzus? Degenerative myelopathy and chondrodystrophy-related intervertebral disc disease are the most common genetic risks by carrier frequency (17.1% and 16.4%, respectively; Donner 2023, n=7527).

Should I do a DNA test on my Shih Tzu? For breeding stock, yes. A panel covering CDDY, SOD1 (degenerative myelopathy), and KLKB1 (prekallikrein deficiency) is essential. Pet owners considering spinal risk can test for CDDY and SOD1 to understand their dog’s genetic background and make informed decisions about exercise and weight management.

What should I feed my Shih Tzu? Feed twice daily to avoid hypoglycemic crashes in this toy breed. Use a complete, balanced kibble with controlled calcium (1.1:1 to 2:1 ratio to phosphorus) during puppyhood. Maintain lean weight throughout life to reduce load on the spine. Quality protein and fat matter more than grain inclusion or exclusion for this breed.

Are Shih Tzus good with kids? Shih Tzus are affectionate and sturdy enough for older children, but the breed’s small size means rough play or drops from height carry risk of spinal injury (given the 16.4% CDDY carrier frequency). Supervision with young children is necessary.

What are the nearest genetic relatives to Shih Tzus? Pekingese, Tibetan Terrier, Tibetan Spaniel, and Pug are among the nearest documented genetic relatives of Shih Tzus (Parker et al. 2017, Cell 169:945-959). Several of these share CDDY risk and toy-breed feeding challenges.

Do Shih Tzus have eye problems? Progressive rod-cone degeneration (prcd-PRA) occurs at very low frequency in Shih Tzus (0.21% carrier frequency, Donner 2023, n=7521). It is not a breed-defining concern, but testing is available if you are screening for all recessive eye variants.

A gift to human medicine

Shih Tzus are a natural model for human disease

Because the same genes cause the same conditions across species, the inherited conditions documented in Shih Tzus help researchers understand, and work toward treating, the human diseases they model. This is the dog advancing human medicine. The breed models the human disease; it does not have it, and this is not a prediction for your dog.

Human equivalents via OMIA → Mondo / OMIM. Model-of, not identity.
Documented in OMIA

Every condition recorded in the Shih Tzu

Beyond the testable carriers above, OMIA's literature catalogue records 19 genetic conditions in the Shih Tzu, 11 of which have a known human equivalent. This is the documented landscape across all Shih Tzus ever studied, not a prediction for any one dog.

Plus 1 more conditions recorded in the Shih Tzu in OMIA.

Online Mendelian Inheritance in Animals (OMIA); Nicholas, Tammen & Sydney Informatics Hub, DOI 10.25910/2AMR-PV70
Documented in the breed's literature is not carrier status and not a forecast for an individual dog. Human equivalents are mapped via Mondo/OMIM. Carrier frequencies (above) are the separately-measured testable subset (Donner 2023).
The data behind this page

Where every number on this page came from.

This page draws on three primary data sources. Carrier frequencies for the Mendelian section come from Donner et al. 2023 (CC-BY-4.0). We grade these data at evidence Limited because the cohort is a direct-to-consumer ascertainment, which biases toward owners who chose to test their dogs. The panel also uses tag-SNP proxies for some variants rather than direct causal-variant assays. Limited is a study-design grade, not a quality grade: the Donner cohort is the largest open canine-genotype dataset in existence and we are grateful for it. We rate the confounding MEDIUM.

Population-genetic dimensions (heterozygosity, intra-breed PCA distance, nearest neighbors, trait-locus frequencies) come from CanVAS (Brundage 2026), harmonized through the Sniff Atlas. The exact release date and verification commit are pinned at the bottom of the page so a researcher can trace a number back to a specific snapshot. The disease-gene-variant graph comes from OMIA (Online Mendelian Inheritance in Animals; Nicholas, Tammen, and the Sydney Informatics Hub at the Sydney School of Veterinary Science, The University of Sydney; retrieved April 2026, DOI 10.25910/2AMR-PV70).

What this page does not yet have. Inheritance modes and per-disease penetrance evidence from Donner 2023 are now in the structured data for every variant the panel covers. Mondo, OMIM, Ensembl, and HGNC cross-references on gene pages remain pending, they arrive in December 2026 alongside the imputed 9.67M-variant CanVAS dataset via the OMIA SQL dump absorption. Until then, gene IDs carry NCBI Gene and OMIA phene URLs only; the wider human-homolog and disease-ontology cross-reference set fills in with that release.

How to cite this page. The computed dimensions on this page are derived from the open Sniff Atlas v1.0.1 (Gehring 2026, doi:10.5281/zenodo.20566358, CC-BY 4.0). Full citation formats including BibTeX, RIS, and CITATION.cff at sniff.world/cite.

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References
  1. Donner J, Freyer J, Davison S, Anderson H, Blades M, Honkanen L, et al. (2023). Genetic prevalence and clinical relevance of canine Mendelian disease variants in over one million dogs. PLOS Genetics 19(2):e1010651. doi:10.1371/journal.pgen.1010651
  2. Brundage J, et al. (2026). CanVAS: a harmonized canine variant atlas. bioRxiv. doi:10.64898/2026.04.13.718238
  3. Nicholas, F.W., Tammen, I., & Sydney Informatics Hub. (2026). Online Mendelian Inheritance in Animals (OMIA) [dataset]. The University of Sydney. https://omia.org. doi:10.25910/2AMR-PV70 (retrieved April 2026).
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Sources: CanVAS (Brundage 2026) · Donner 2023 · OMIA