Typically the mutated gene is involved in developmental patterning, and a syndrome of congenital anomalies results, of which polydactyly is one feature or two.Polydactyly has been linked to the prenatal environment, however, with a recent study showing a relationship to maternal pollution exposure in China.Types include:

97 genetic syndromes have been associated with different kinds of polydactyly. Ulnar polydactyly
Ulnar polydactyly is often bilateral and associated with syndactyly and polydactyly of the feet. This can be a simple or complex polydactyly. Ulnar polydactyly occurs as an isolated congenital condition, but can also be part of a syndrome. The syndromes which occur with ulnar polydactyly are: Trisomy 13, Greig cephalopolysyndactyly syndrome, Meckel syndrome, Ellis–van Creveld syndrome, McKusick–Kaufman syndrome, Down syndrome, Bardet–Biedl syndrome, Smith–Lemli–Opitz syndrome

Radial polydactyly
Type VII of radial polydactyly is associated with several syndromes:
Holt–Oram syndrome, Fanconi anemia (aplastic anemia by the age of 6), Townes–Brocks syndrome, and Greig cephalopolysyndactyly (also known to occur with ulnar polydactyly). Central polydactyly
The syndromes associated with central polydactyly are:
Bardet–Biedl syndrome, Meckel syndrome, Pallister–Hall syndrome, Legius syndrome, Holt–Oram syndrome. Also, central polydactyly can be associated with syndactyly and cleft hand. Other syndromes including polydactyly include acrocallosal syndrome, basal cell nevus syndrome, Biemond syndrome, ectrodactyly-ectodermal dysplasias-cleft lip/palate syndrome, mirror hand deformity, Mohr syndrome, oral-facial-digital syndrome, Rubinstein-Taybi syndrome, short rib polydactyly, and VATER association. It can also occur with a triphalangeal thumb. Diagnosis
Classification is performed by using x-ray imaging to see the bone structures. Ulnar polydactyly
The classification of ulnar polydactyly exists of either two or three types.
A 2022 systematic review brought together evidence from 11 studies that compared dressings and topical agents for treating open wounds after surgical treatment for pilonidal sinus of the buttocks. The authors concluded that: platelet rich plasma may help wounds to heal quicker compared to sterile gauze; Lietofax skin repair cream may help wounds to heal by 30 days compared to iodine (which helps to reduce bacteria in the wound); but it is not clear whether hydrogel dressings (designed to keep the wound moist) reduce the time it takes wounds to heal compared with cleaning the wound with iodine. Etymology
Pilonidal means nest of hair and is derived from the Latin words for hair (pilus) and nest (nidus). The condition was first described by Herbert Mayo in 1833. R.M. Hodges was the first to use the phrase pilonidal cyst to describe the condition in 1880.The condition was widespread in the United States Army during World War II. The condition was termed "Jeep seat" or "Jeep riders disease", because a large portion of people who were being hospitalized for it rode in Jeeps, and prolonged rides in the bumpy vehicles were believed to have caused the condition due to irritation and pressure on the coccyx. References
External links

NHS Choices for pilonidal sinus treatment