Persian and exotic shorthaired cats are especially susceptible to a genetic kidney disorder known as Polycystic Kidney Disease (PKD). The same dominant gene occurs in dogs, other animals, and humans. Research began in the 1990s using female Persians as the test subject.
Causes
Even though kittens are born with cysts, the disease is slow to manifest and causes enlarged kidneys and kidney dysfunction in older Persians of seven years of age and older.
In the beginning of the cyst formation, they are small, no larger than a centimeter or so. The cysts at this point do not seem to pose a problem in kittens but as the cats age, the cysts become much larger. The kidneys enlarge as the cysts enlarge. The cysts also grow in numbers as well as size. The kidneys are taxed to the point that they can no longer function normally and shut down which ultimately causes renal failure.
Symptoms
Reduced energy
Vomiting
Depression
Lack of appetite
Excessive thirst
Frequent urination
It is important to note that cats can die of other causes before they succumb to kidney failure.
Diagnosis
The most affective diagnostic test to date is the ultrasound, which will indicate the presence of the cysts within the kidneys.
Frozen sections of the kidneys are taken from deceased cats to test for the presence of cysts. It is also possible to remove a kidney (nephrectomy) for examination.
Polycystic kidney disease is the presence of cysts in the renal cortex. But the cysts can also be presence in the medulla (soft marrow -like inside center) of the kidney. If they are found elsewhere, the cat would not be diagnosed as having this specific disease.
Treatment
There is no known treatment to date that will reduce or rid the cat of these cysts.
However there are three tests that are currently in the research phase of development:
A soy protein diet
Potassium Citrate treatment
Drug - "epidermal growth factor receptor, or EGFR" to prevent the growth of these cysts.
Prevention
An ultrasound will confirm the autosomal (not sex linked) gene causing the problem. Breeders can help eliminate the problem by spaying and neutering the affected cats and breeding only those cats that do not carry the gene. That way the new populations of Persians and exotic shorthairs will be clean and problem free.
If one cat is Polycystic free and the other mate is heterozygous meaning it has only one chromosome passed down from its parents causing the problem, the two new mates can still have some normal kittens. How it works is that the polycystic free gene can only donate that gene to its offspring, while the other cat who has both a free and affected chromosome and can donate either to their offspring. If the cat donates the free gene the kittens then they will not contract the Polycystic Kidney Disease.
This option may be more viable to the breeder if the stud or queen in question is very valuable.
A concerned Persian or exotic shorthaired cat owner can ask for the complete cat history of the parents which includes their genetic history and the cat owner can also have an ultrasound done to make sure, their cat is polycystic free.
Prognosis
Unfortunately, there is no cure available for Polycystic Kidney Disease to date. Affected cats will die around seven years of age, however it has been noted that indoor cats can live longer lives. It is also noted that some cats die of other diseases before kidney failure ever occurs.
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