The condition seems to be most commonly found in cats along the East Coast of North America (in the United States and Canada) and in South West England, Wales and Kingston-upon-Hull.
Polydactyly is most commonly found on the front paws only it is rare for a cat to have polydactyl hind paws only, and polydactyly of all four paws is even less common. Various combinations of anywhere from four to seven toes per paw are common. Both Jake, a Canadian polydactyl cat, and Paws, an American polydactyl cat, were recognised by Guinness World Records as having the highest number of toes on a cat, 28. Normal cats have a total of 18 toes, with five toes on each fore paw, and four toes on each hind paw polydactyl cats may have as many as nine digits on their front or hind paws. The SHH protein is an important signalling molecule involved in patterning of many body elements, including limbs and digits. Some cases of polydactyly are caused by mutations in the ZRS, a genetic enhancer that regulates expression of the sonic hedgehog (SHH) gene in the limb. Polydactyly is a congenital abnormality that can be inherited in an autosomal dominant manner.