Genetic basis of Polycystic Kidney Disease in cats - is primarily caused by a mutation in the PKD1 gene. This gene encodes polycystin-1, a renal tubule membrane glycoprotein critical for epithelial cell proliferation and differentiation in the kidneys. The disease is inherited in an autosomal dominant manner, meaning that only one copy of the mutated gene from either parent is enough to cause the disease. There are no healthy carriers; every cat with the mutated gene will develop PKD. Homozygous mutations are likely lethal embryonically, so affected cats are heterozygous for the mutation. The PKD1 mutation identified is a nonsense mutation causing polycystic kidney disease, with nearly complete penetrance.
Pathophysiology - PKD causes the formation of multiple fluid-filled cysts within the renal cortex and medulla, sometimes also affecting the liver and pancreas. These cysts are congenital and present from birth but enlarge progressively, displacing normal kidney tissue. Over time, this leads to tubulointerstitial inflammation and fibrosis, causing a decline in kidney function and ultimately chronic kidney disease or kidney failure. Cysts can also occasionally form in other organs such as the liver. The progression and severity are variable between individual cats.
Complications - Progressive renal failure, typically developing around 7 years of age on average, but severity and rate vary widely. Hepatosplenomegaly or cysts in other organs like the liver. Secondary complications of kidney failure, including decreased kidney function and eventual death. Some cats may develop cardiac abnormalities related to the disease. Kidney failure can occur anywhere from young adult cats to late in life, with some cats succumbing early at 2-3 years.
Why This Matters to Breeders and Vets - PKD is particularly common in Persian cats and breeds derived from them (e.g., Exotic Shorthair, Himalayan, Scottish Fold, British Shorthair). Breeders need to perform genetic testing to identify affected and carrier animals to prevent passing the mutation to offspring and reduce disease prevalence. Early diagnosis through genetic testing or ultrasound screening (usually after 10 months of age) helps monitor and manage the condition. Since the disease often has late onset, affected cats may be bred before symptoms appear without testing, perpetuating the gene in populations. Vets play a key role in advising breeders and managing affected cats, providing supportive care for kidney disease and associated complications.
Summary - Polycystic Kidney Disease (PKD) in cats is an autosomal dominant inherited disorder caused primarily by a mutation in the PKD1 gene, leading to the development of multiple cysts in the kidneys and sometimes other organs. The cysts grow over time, replacing normal kidney tissue and resulting in chronic kidney disease and potentially kidney failure. The disease is prevalent especially in Persian and related breeds. Genetic testing and ultrasound screening are essential tools for early diagnosis and management and help in breeding decisions to control disease incidence and improve feline health outcomes.