Polycystic Kidney Disease (PKD)

Polycystic kidney disease is one of the most common inherited disorders in pedigree cats, affecting an estimated 30–40% of Persians worldwide before DNA testing became widespread. The same mutation appears in breeds developed from Persian lines, including Himalayans, British and Exotic Shorthairs, Scottish Folds, Chartreux and Burmillas.

The disease is caused by a single dominant mutation in the PKD1 gene. Because it is dominant, a kitten that inherits just one copy from either parent will develop cysts — there is no “silent carrier” state. The cysts are microscopic at birth but grow steadily throughout life, expanding from pinpoint size to fluid-filled sacs up to a couple of centimetres across. As they enlarge they compress and destroy the surrounding healthy nephrons.

For years the cat shows no outward signs. Most affected cats are not diagnosed until middle age, around seven years, when enough kidney tissue has been lost to cause chronic kidney disease. At that point the signs are identical to CKD: increased thirst and urination, weight loss, a dull coat, reduced appetite and intermittent vomiting.

Diagnosis is straightforward. Abdominal ultrasound reveals the characteristic cysts and is reliable in cats over about 10 months old. Even better, a DNA test can confirm the PKD1 mutation in a kitten of any age from a simple cheek swab, allowing breeders to make informed decisions and owners to monitor at-risk cats early. While there is no cure, the same supportive care used for chronic kidney disease — a phosphorus-restricted renal diet, blood-pressure medication, and good hydration — can give affected cats many comfortable years.