Congenital Defects in Cats
By Stephen M. Sheldon, DVM

A congenital defect is more commonly known as a birth defect. Most are present at or near birth. However, it is interesting to note that many congenital defects do not manifest themselves until well after birth. An example of this would be congenital heart defects in people; while the defect is present at birth, many times heart problems, such as a cardiomyopathy, may not show up until later in life. In this article, we’ll discuss some of the more common defects, starting, of course, at the front end of the cat!

Eyes and Eyelids
Many Persian and Himalayan cats are born with a condition called entropions in which the eyelids roll inward causing irritation to the cornea, or clear part of the eye. Corneal ulcers often result and can be difficult to control. Usually the lower lid is affected but entropions can be seen in either lid. They can be managed with topical ointments until surgery can be performed to correct the defects. It is best to wait until your cat is fully-grown before surgery, but we don’t always have this luxury.

Cataracts are another common congenital disorder of the eyes. It is usually present at birth but often goes unnoticed until 6-8 weeks of age (anyone who notices it before 2 weeks of age automatically receives the Veterinarian of the Year award). It has been noted to occur in Domestic Short and Longhaired cats, Persians, Birmans, and Himalayans. These cataracts may undergo spontaneous resorption within the first year (i.e., disappear); if not, and if the retina is working, surgery may be needed.

Degeneration of the retina has been reported in Siamese, Persian, and Abyssinian cats. This disease starts gradually as small spots on the retina and progresses to cause blindness. There is no treatment.

Ear, Nose, and Throat
Nasopharyngeal polyps originate from the mucosa, or lining, of the nasal cavity, the middle ear, or the auditory tube. They cause difficult breathing, sneezing, nasal discharge, voice change, and difficulty in swallowing. If they affect the middle ear, they can cause head tilts and problems with balance. They are found by examining the nasal passages under anesthesia and treatment requires removing them surgically.

Cleft palates and cleft lips commonly affect Siamese cats and are easily identified by a physical exam. They can be treated surgically, or if they are a cosmetic defect only they can be left as is. Cleft palates require correction in most cases.

Megaesophagus is another defect involving mainly Siamese cats, although it is seen in other breeds as well. The most common symptom is regurgitation. Regurgitation is different from vomiting in that the food is completely undigested and the event occurs immediately after eating. This is usually caused by a motor disturbance. We mange this disease by using different types and methods of feeding. Some drugs that increase motility in the esophagus can also be tried.

Neurologic
There are a number of neurologic defects affecting cats. Spina bifida is seen in Manx and Siamese cats. Affected cats can have portions of the spinal cord showing and may be missing their tails. In addition, they have problems controlling urination and defecation. Cerebellar diseases like neuaxonal dystrophy affect coordination and show up when kittens are 5-6 weeks old; they are seen mostly in the tri-color breeds. There is no treatment; some cats progress to the point where they must be euthanized, others become static, getting neither better nor worse. You are just left with a very uncoordinated, but otherwise normal kitty (my friend had one in Veterinary School). Vestibular defects manifest in a very similar way and are seen in Siamese and Burmese cats.

Liver
I move to liver next because a common congenital defect in cats, the portosystemic shunt because it produces symptoms often confused with neurologic disease. It occurs because veins that are supposed to carry blood through the liver are malformed. It is seen in Long/Shorthaired domestics, Himalayans, Persians, and Siamese cats. Cats often vomit, drool, and seem very disoriented. A shunt can be corrected surgically, although the surgery is more successful in dogs than cats.

Cardiac
Patent ductus arteriosus (PDA) is a disease seen in Persian and Siamese cats (as well as humans!). It occurs when a blood vessel in the fetus (the ductus arteriosus) does not close shortly after birth. PDA is often associated with defects of the heart valves and the septa too (the septa are the walls between the left and right sides of the heart). Surgery is required to correct a PDA.

Cardiomyopathies in cats are thought and known to be hereditary - that is they are passed on from generation to generation. They are not considered a congenital defect. In other words, there isn’t any damage present at birth.

Miscellaneous
Believe it or not, cats also suffer from Hemophilia-especially Siamese. Domestic Shorthairs, and British Shorthairs. The disease is very similar to the disease seen in people. Some cats also suffer from hip dysplasia; again, this is very rare. Some other uncommon congenital defects reported are seborrhea oleosa, amyloidosis, and mucopolysaccharidosis.

A common grain in most of these congenital problems seems to be that the patients are purebred cats, notably Siamese, Persian, and Himalayans. My clinical experiences parallel these too, so I guess it is true what they say about purebred cats! The best safeguard you as a new cat owner can have is to get your cat examined soon after purchase by a Veterinarian and insist on thoroughness!