There are plenty of health conditions that humans and dogs have in common. For example, our canine companions can contract diabetes, cancer, and epilepsy. They can even develop similar mental health illnesses to humans, such as anxiety.

Down syndrome is one of the most common genetic conditions affecting humans, causing delays in growth, learning difficulties, and distinctive facial features. Whether or not dogs can also develop this chromosomal disorder is a controversial topic requiring further research.

What is Down Syndrome?

Down syndrome is caused by an extra full or partial copy of chromosome 21 in humans. This means that people with the condition have extra genetic material in their DNA, giving them the characteristics of Down Syndrome.

Around 1 in every 700 babies born in the USA is born with Down Syndrome.

dog down syndrome SolStock / Getty Images


Canine and Human Genetics

There are many genetic similarities between humans and dogs. However, there are key differences when it comes to the number of chromosomes in our DNA. Humans have 23 pairs of chromosomes while dogs possess 39. So, it's unclear whether a change in chromosome 21 would have the same effect in dogs as it does in humans.

woman gently caresses her dog


Can Other Species Get Down Syndrome?

One piece of evidence which could potentially support the possibility of Down Syndrome in dogs is the fact that it can exist in mice. As part of their research into Down Syndrome, scientists have been able to alter the genetics of mice, so they carry an extra copy of their chromosome 16, which is comparable to chromosome 21 in humans.

This chromosomal change causes symptoms in mice similar to those of Down Syndrome in humans. However, this has only ever been observed in mice genetically engineered in the laboratory.

mice laboratory chromosome down syndrome D-Keine / Getty Images


Down Syndrome Symptoms

People with Down Syndrome typically have facial features characteristic of the condition. These include a flattened face, slanted eyes and smaller ears than average. The condition also causes learning difficulties, although this varies in degree widely between individuals.

Down Syndrome often causes medical issues. Most commonly, people with the condition also experience loss of hearing, sleep apnea, and congenital heart defects.

down syndrome symptoms people manonallard / Getty Images


Down Syndrome in Dogs

There have been no proven cases of Down Syndrome in dogs. If it does exist, it occurs far more rarely than it does in humans.

It may be the case that dogs simply never get Down Syndrome. However, it is possible that cases of the condition in dogs are missed because it isn't routinely tested for. It could also cause the death of affected dogs before the condition can be diagnosed.

dog Down Syndrome condition marcoventuriniautieri / Getty Images


Congenital Hydrocephalus

Congenital hydrocephalus is a condition sometimes mistaken for Down Syndrome in dogs as it mimics many of the symptoms. A dog may be born with the condition or develop it later as the result of a tumor, bleeding, or inflammation of the brain.

The symptoms of congenital hydrocephalus in dogs include a dome-shaped head, learning delay and reduced eyesight

hydrocephalus dogs brain symptoms designer491 / Getty Images


Pituitary Dwarfism in Dogs

Pituitary dwarfism is another condition causing symptoms similar to Down Syndrome in dogs. It occurs when the pituitary gland in the brain fails to produce adequate growth hormone. When a puppy is first born, it shows no signs of the condition. However, it becomes apparent when the puppy doesn't grow at the same rate as its siblings.

Although it may cause the dog to appear to have Down Syndrome, pituitary dwarfism is an inherited condition with a proved genetic cause.

Cute homeless puppy. Need for home


Congenital Hypothyroidism

If a dog has a condition called congenital hypothyroidism, it may exhibit some of the symptoms associated with Down Syndrome. This is because its thyroid gland doesn't produce enough of the hormones it should. This can cause learning delay, dwarfism, and a broad, flattened skull. However, congenital hypothyroidism is not related to Down Syndrome.

congenital hypothyroidism dogs symptoms juststock / Getty Images


Caring For a Dog With Special Needs

Although it's unclear whether dogs can have Down Syndrome, any animal exhibiting similar symptoms will need to be carefully looked after. It's important to take them to see a veterinarian regularly to make sure they are healthy.

Additionally, a dog with developmental delays or impaired eyesight will need a home environment free from hazards and obstacles. A balanced and nutritious diet will also help a dog with special needs to function at their optimal level.

special needs dog care healthy iamnoonmai / Getty Images


When To Consult a Veterinarian

Whether or not Down Syndrome truly exists in dogs, it's important to take them to see a veterinarian if they are displaying any of the symptoms. This could mean that they have one of the genetic conditions that produce similar symptoms to Down Syndrome.

Symptoms requiring assessment by a vet include an abnormally-shaped skull, slow growth, problems with hearing or eyesight, developmental delays and muscle weakness.

dog veterinarian symptoms Down Syndrome shironosov / Getty Images


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