Down syndrome in dogs: Does it exist and what can resemble the condition?

Puppy chewing on rope toy
(Image credit: Getty Images)

Does down syndrome in dogs exist? Sometimes, it’s easy to tell whether your pet is unwell, especially with physical symptoms like vomiting, diarrhea, itching, or coughing. Even with behavioral symptoms like panting, anxiety, or aggression, you’d probably spot the signs and realize you need some expert advice. 

However, what if the symptoms are more unusual, subtle, or vague? After all, how do you know if your dog is sick or if they are acting and developing normally? This might be why pet parents often wonder whether conditions like autism and down syndrome exist in dogs.

While dogs can’t get down syndrome, they can exhibit signs and symptoms that are consistent with this condition. 

Below, we walk you through everything you need to know, including some of the similar symptoms and the conditions that can resemble down syndrome in dogs. 

What is down syndrome?

Down syndrome is a genetic condition that affects around 1 in 700 human babies. Most people have 23 pairs of chromosomes, made up of genetic coding that correlates with hair colour, eye colour, and other inherited traits. People with Down Syndrome have an extra chromosome 21 as a complete or partial copy.

Although people with down syndrome share the same type of genetic abnormality, the physical attributes and intellectual impact of down syndrome are very variable.

However, some physical features associated with down syndrome, to some degree, are smaller ears, a less prominent nose bridge, a flatter face, and a protruding tongue. Small hands and feet, a shorter neck, and shorter general stature are also common. 

Sadly, those with down syndrome are more at risk of mental health issues like depression, anxiety, and obsessive-compulsive disorders. 

Can dogs get down syndrome?

The simple answer is that dogs can’t get down syndrome, although they can show signs and symptoms that are consistent with or similar to the condition. They can also get other genetic disorders and chromosomal abnormalities, but not Down Syndrome. 

You might wonder how we know that dogs don’t get down syndrome. After all, surely we’d only know if we tested for it, which we don’t. Well, there are a few reasons why we are confident that dogs can't get down syndrome. 

Firstly, dogs don't have the same number of chromosomes as us, and their genetic makeup is not the same. Therefore, an additional chromosome 21 would not have the same effect. Equally, if a dog did have a chromosomal abnormality similar to down syndrome, it likely wouldn’t survive.

Dog lying on couch

(Image credit: Getty Images)

Down syndrome-like signs in dogs

While dogs can't get down syndrome, a few health conditions cause similar signs. So, what symptoms or signs can dogs get that might seem similar to Down Syndrome in people? Firstly, dogs may be slow to grow or have stunted growth, leading to a smaller stature when they are adults. 

It's important to remember that down syndrome has a very variable effect on people's intellectual ability and cognitive function. However, all people with Down Syndrome have some degree of limitation, even if it is very mild. Dogs can also get cognitive dysfunction, sometimes due to brain degeneration as they are older or abnormal development when they are young.

Conditions that resemble down syndrome in dogs

Conditions like Pituitary Dwarfism, Congenital Hypothyroidism, Portosystemic Shunt, and deficiencies in Growth Hormone can all cause reduced growth and small stature, similar to Down Syndrome. 

For some conditions, the similarities don't end there. Congenital Hypothyroidism doesn't just affect the dog's size; it also affects their brain function and development while causing them to have short limbs and a large, prominent tongue. Similarly, a dog with Portosystemic Shunt could experience changes in behaviour and brain function associated with the build-up of toxins in the blood.

Finally, congenital conditions affecting the brain, including hydrocephalus, where the head is domed, and the brain is full of fluid, can cause limitations in cognitive function. In some cases, this may create the illusion that they have a condition like down syndrome.

How to care for a down syndrome dog

Dogs can't have down syndrome, but other conditions can sometimes mimic similar signs. If you're worried about your dog's growth or think they are not developing as they should, you should speak to your veterinarian. 

This is especially important if they are showing other signs of being unwell, neurological signs, or struggling with cognitive function. Examples of poor cognitive function might be failing or being slow to respond to you or other stimuli like toys, people, and other animals. Or you might notice that your canine companion is hard to train, hyper, distracted, or vacant.

Your veterinarian can recommend tests that could help find the underlying cause. Once the cause is known, they can prescribe treatment or advise you on how best to support your dog and give them a good quality of life.

Summary

Although down syndrome doesn't occur in dogs, they can get other developmental and congenital conditions. These can cause signs like stunted growth, poor brain development, or reduced cognitive function. So, if you have any concerns about your dog’s development, you should speak to your veterinarian. 

Dr Hannah Godfrey is a small animal vet with a love of dentistry and soft tissue surgery. She lives in Wales with her partner, son, and their two cats.