Can Dogs Have Down Syndrome?
Down syndrome is a set of physical and mental symptoms caused by a genetic disorder and, although it is common to find it in the human population, it does not occur in the same way in other species. If you’ve ever wondered, no, dogs can’t have Down syndrome.
Although some puppies can show similar symptoms, its cause has another explanation. Humans and dogs share many genetic disorders, but Down syndrome is not among them.
What is Down syndrome?
When we talk about any syndrome, we are referring to a set of symptoms characteristic of one or several diseases. Down syndrome is known for a series of symptoms:
- Recognizable facial features: Flat face, especially the bridge of the nose, with small almond-shaped eyes, short neck and small ears.
- Different degrees of intellectual disability.
- Low muscle tone or flexible ligaments.
- Hearing loss and tendency to ear infections.
- Eye diseases such as cataracts or nearsightedness.
- Sleep apnea.
- Heart problems.
- Other common problems: intestinal obstructions, anemia, thyroid problems, leukemia, Hirschsprung’s disease…
The cause of the syndrome is in the chromosomes: we humans have 46 chromosomes. Of these 46 chromosomes, half is provided by the sperm at the time of fertilization, while the other half is provided by the egg.
The cells of people with Down syndrome have an extra chromosome in their nucleus, 47 chromosomes instead of 46. This is an extra chromosome 21, making the alteration also known as trisomy 21.
Each species, animal or non-animal, has a specific number of chromosomes, the way DNA condenses inside cells.
The division of chromosomes occurs in the same way in other animals, such as dogs, for example. In other words, it is possible that there is a trisomy in a pair of chromosomes, but not Down syndrome.
Can dogs have Down syndrome?
Only in non-human primates, with which we share 98% of the genetic information, has a similar syndrome been found, but this has not occurred in other species, such as dogs or cats. However, they can suffer from other genetic abnormalities that share some of their symptoms.
Certainly, you’ve already seen fake news circulating on the internet about Down syndrome in cats, tigers, dogs… accompanied by photos with features that remind us of the features of Down syndrome. The origin of these traits can be in a deformity, a disease or a genetic alteration, but not in Down syndrome.
The most similar syndrome in animals was identified thanks to a strain of laboratory rat, the trisomic rat, which researchers created to study Down syndrome in an animal model.
From the mouse chromosome 16, they managed to create a trisomy with genes from chromosome 21 in humans. The objective is to study the expression of these gene copies and their similarity to Down syndrome, the interaction between genes and, furthermore, to favor the development of a possible future gene therapy.
Genetic Diseases in Dogs
It is possible that animals also suffer from intellectual disability, but it is something different from trisomy 21, which can occur due to different factors. For example, the syndrome of cognitive dysfunction occurs in older dogs – can occur in cats, but it is much less clear – and arises due to old age.
We share many other genetic diseases with dogs, some of which are the result of mutations in specific chromosomes, such as night blindness, cataracts or even narcolepsy, which makes certain breeds good models for studying these diseases in humans.
