Accessory digit =الاصبع الزائد |
Supernumerary Digit Polydactyly is the most common congenital digital anomaly of the hand and foot. It may appear in isolation or in association with other birth defects. Isolated polydactyly is often autosomal dominant or occasionally random, while syndromic polydactyly is commonly autosomal recessive. Polydactyly should not be considered as a single mendelian trait but rather multifactorial. Early theories for polydactyly concerned disorders in the programmed cell death cycle of fetal limb development. Current theories focus on mutations in specific genetic locations that cause limb development to go awry. Mammals have been shown to have genetic clusters identified as homeobox or Hox genes corresponding to 5 domains across the limb bud. According to Muragaki et al, mutations in the HOXD13 gene are associated with synpolydactyly. As limb growth in utero progresses along a preset time line, elongation of the limb, development of soft tissue, and differentiation of digits progresses. The epidemiologic data on postaxial polydactyly is limited because most birth defect registries do not include them, preferring to focus on defects linked to teratogens. Despite being a common malformation, the true incidence of polydactyly is not fully known. One study by Finley et al combined data from While the incidence of preaxial and postaxial polydactylies has been investigated, central polydactyly has not been fully studied. Genetic and ethnic factors greatly influence the nature of polydactyly in the world population. Unfortunately, the knowledge of polydactyly is limited to select studies of certain subpopulations. Preaxial polydactyly is very common in various Asian populations, accounting for 90% of cases in South China, Hong Kong, and Postaxial hand polydactyly is a common isolated disorder in African black and African American children, and autosomal dominant transmission is suspected. Postaxial polydactyly is approximately 10 times more frequent in blacks than in whites and is more frequent in male children. In contrast, postaxial polydactyly seen in white children is usually syndromic and associated with an autosomal recessive transmission. Other factors associated with postaxial hand polydactyly include male sex, twinning, low maternal education, parental consanguinity, and recurrence in first-degree relatives. Postaxial polydactyly is associated with Amerindian, parental subfertility, and bleeding in the first trimester. Polydactyly is the most common congenital digital anomaly of the hand and foot. It may appear in isolation or in association with other birth defects.
Treatment Surgical management depends greatly on the complexity of the deformity. Postaxial polydactyly of the foot most commonly is treated with surgical removal for cosmesis and shoe comfort. Waiting until age 9-12 months is advisable to decrease anesthesia risk. A related eMedicine article is Polydactyly of the Foot.
A child with distal extremity anomalies experiences emotional stress. By age 3 years, the child has become aware of the anomaly. By age 7 years, the child has begun to experience the close scrutiny of his peers at school. For these reasons, as well as others, surgical correction should be initiated early in life. Needless to say, psychological support should be provided for patients and parents facing these challenges.
|