Polydactyly is a genetic condition which manifests in the form of extra fingers and toes. These digits are sometimes called supernumerary, in a reference to the fact that they exceed the number of conventional digits. Polydactyly is not life threatening or harmful, although it may be associated with a more serious genetic condition which does require treatment. In some parts of the world, people choose to remove these excess digits to avoid comment or social isolation.
These extra digits can take a number of different forms. The most common is a stub of tissue without any joints, typically located next to the little finger or toe. In some cases, however, the extra digit has bones and articulated joints, and it can even be used. This can cause x-rays to look quite unusual and sometimes a bit confusing. Some people have polydactyl thumbs, meaning that they have two thumbs on the same hand, typically right next to each other.
The condition is caused by an error in the genes which determine the shape of the hand or foot. In some cases, it's an isolated genetic incidence, and the polydactyly is the only symptom. In other instances, something goes awry during fetal development, causing genes to misfire and grow another digit. In other instances, the condition may be part of a larger genetic condition such as aneuploidy, an odd number of chromosomes which can lead to serious birth defects.
The only treatment for polydactyly is surgery. Since the condition is not harmful, most surgery is cosmetic, although in some cases the extra digits may interfere with normal life. Some people choose to retain their polydactyly, and other than trouble finding gloves that fit, the condition is usually not an issue. However, in some areas birth defects are treated with serious superstition; deformities are treated as curses and they are associated with Satan and evil doings. In these cases, surgery is a good choice, because it will allow the patient a much happier life.
Many people are familiar with polydactyly in cats, since it is a rather common mutation, especially along the East Coast of the United States. A polydactyl cat may have one or more extra toes on each foot, causing the feet to appear large and splayed. The Hemingway cats in Florida, who live on the former estate of Ernest Hemingway, are well known polydactyl cats, demonstrating the genetic link to polydactyly in cats as they represent multiple generations of felines.