Cat With Down Syndrome

What is Cat With Down Syndrome?

Down’s Syndrome is one of the most common genetic conditions, caused by abnormality in the normal chromosomal count in humans. This disease belongs to a group of genetic disorders called trisomias (like Edwards syndrome, Triple X syndrome). Usually humans have 23 pairs of chromosomes- 22 pairs of somatic and 1 pair of sex chromosomes), making it total 46 chromosomes. People with this genetic condition have an extra 21 chromosome present in some or all the cells in the body. Having this extra chromosome causes changes in the normal development of fetus, causing a wide range of symptoms ^[1].

Can cats have Down Syndrome?

Down’s syndrome refers to trisomy of the 21^st chromosome. Cats usually have only 19 pairs of chromosomes, 18 somatic and 1 pair of sex chromosomes, making the total count 38. This means, that Cats don´t have 21^st chromosome trisomy, but there have been cases of cats having defects at birth, that resemble the symptoms of Down´s syndrome in humans. In fact, cats can and often have genetic disorders ^[2].

Trisomy 21 symptoms

Down’s syndrome presents with some typical characteristics when the baby is born, like:

• Decreased muscle tone after birth
• Flattened facial features in profile, flattened nose
• Small head, ears and mouth
• Short neck with extra skin on the back (similar to Turner´s syndrome )
• Eyes are located further from each other than normally, in an upwards angle. An extra skin fold can cover the inner angle of the eye
• Short hands and fingers

The cognitive and physical development of the child can be impaired. It takes longer for children with Down´s syndrome to learn how to crawl, walk, talk and do any other activities ^[3].

There are also a number of conditions that are associated with Down´s syndrome:

• Congenital heart disease
• Hearing impairment, ranging from minor to complete hearing loss
• Vision impairment- cataract might be present at birth or develop later in life, strabismus (crossed eyes), myopia
• Immune system disorders, commonly occurring infections
• Hypothyrodism
• Predisposition to develop leukemia, anemia and polycythemia
• Skeletal disorders- atlanto-axial instability- disturbance in the normal development of the spine, that can cause spinal cord injury
• Epilepsy
• Mental health problems^[3]

Similar symptoms are presented in various other chromosomal disorders, like Mowat Wilson syndrome therefore the definite diagnosis can only be made after chromosomal analysis.

What Causes Down Syndrome?

The exact cause for Down´s syndrome is still unknown. In humans there is a link between mother´s age and the risk of her child having Down´s syndrome. By the age of 35, the risk of having a child wit trisomy 21 is 1 in 350; by the age of 40 the risk dramatically increases to 1 in 100. If the mother has already has a child with Down´s syndrome, the risk of having another child with this syndrome is around 1 in 100 ^[4].

Types

There are 3 types of this syndrome, that each have a different presentation

Nondisjunction (trisomy 21)

An error in the process of cell division results in an embrio with 47 chromosomes, instead of 46. This is the most common type of Down´s syndrome, accounting for 95% of cases

Mosaic Down syndrome

occurs in around 1% of all cases. Some of the cells have 47 chromosomes (with extra 21 chromosome), while other cells have a normal chromosome count.

Translocation

All cells have a normal chromosomal count- 46, but in the cell division process some partial or full copies of 21 chromosome attaches to another chromosome, causing the typical symptoms. Usually the 21 chromosome attaches to the 14^th. This occurs in around 4% of all cases ^[5].

Symptoms

Symptoms that a cat with Down´s-like syndrome might present are:

• Eyes set further apart from each other than normally
• Stunted or flabby ears
• Flattened or upturned nose
• Different behavior compared with other cats
• Motor dysfunction, poor muscle tone
• Heart problems
• Hearing loss
• Vision defects^[2]

Special needs cats

There hasn´t been a lot of research done on the chromosomal conditions of cats. It is possible for cats to have Down´s syndrome like disorder. Still, there are also some other diseases that can cause similar symptoms. Some owners associate their cat’s behavioral differences with Down´s syndrome. It can also be a symptom of another disease. One of the most common complaints from pet owners is the facial features, which resemble Down´s syndrome. Another disease that can cause similar facial features is Klinefelter syndrome, which can be present in cats.

To avoid genetic disorders in cats, breeders have to pay extra caution. If two cats from the same family are bred, they might pass a recessive gene to their offspring, causing various genetic conditions. The risk is lower if cats from two different lineages are bred ^[2].

Famous cat with Down Syndrome

Kitten Otto was a nationwide sensation in Turkey. He was believed to be the first cat with Down´s syndrome in Turkey. The precise diagnosis was never made, but since the cat had facial features resembling Down´s, it was assumed that he suffers from this disease. Unfortunately the cat passed away due to heart failure ^[6].

Monty, the star of social media is a cat in Denmark. This cat presented with classic facial features of Down´s, urine incontinence, behavioral changes. Monty has his own Facebook page with purpose of raising money for cat shelters in Denmark^[7].

Max the Ginger was already quite old when he was diagnosed with feline Down´s syndrome. The cat had underdeveloped lower part of the brain, causing him to be clumsy, out of focus and lose the control of motor functions. His symptoms got worse with time ^[2].

References

1. http://emedicine.medscape.com/article/943216-overview?pa=DxCEYThPwwzmLABpGF%2B%2FEwR6nM%2BrKfhDnfSVUkm9yZwpZQnlTTkVyNS11dIPeG1gcFrqow%2Bf2%2F37XuRaZT6JAA%3D%3D
2. https://pethelpful.com/cats/Can-Cats-Have-Down-Syndrome-The-Lowdown-on-Feline-DS
3. https://www.nichd.nih.gov/health/topics/down/conditioninfo/pages/symptoms.aspx
4. http://www.mayoclinic.org/diseases-conditions/down-syndrome/basics/risk-factors/con-20020948
5. http://www.ndss.org/down-syndrome/what-is-down-syndrome/
6. http://www.hurriyetdailynews.com/turkey-mourns-for-otto-the-kitten-diagnosed-with-downs-syndrome.aspx?PageID=238&NID=69085&NewsCatID=378
7. http://en.newsner.com/meet-monty-the-cat-with-downs-syndrome-that-has-captured-hearts-around-the-world/about/wow,family,animals