Polydactyly

General description

In general, dogs have five digits on their front paws and four digits on their hind paws presumably due to evolutionary adaptation in which the first digit of the hindlimb was lost. Polydactyly (also known as canine preaxial polydactyly or PPD) describes the restoration of the first digit in the hindlimb (hind dewclaw). Polydactyly in many breeds is associated with a genetic variant of the LMBR1 gene that is inherited in an autosomal dominant manner. The genetic variant does not impact the expression of LMBR1 but impacts a conserved region in the canine genome (ZPA regulatory sequence) that is involved in regulating the expression of other genes, like the sonic hedgehog (SHH) gene, responsible for limb development. Dogs with one or two copies of this variant are likely to have polydactyly or hind dewclaws.

Please note: Polydactyly in the Great Pyrenees is associated with a genetic variant of the ALX4 gene which cannot be detected by this test.