Polydactyly in the American Indian.
Polydactyly has an incidence in the American Indian twice that of Caucasians. A minimum estimate of this incidence is 2.40 per 1,000 live births. Preaxial type 1 has an incidence three to four times that reported for Caucasians or Negroes. The overall sex ratio in Indians is distorted with more males affected than females. The preaxial type 1 anomaly has a strong predilection for the hands and always is unilateral in contrast to postaxial type B where more than one-half are bilateral. The evidence to date, consisting of varying incidences of specific types of polydactyly among American whites, Negroes, and Indians in varying enviroments, suggests different gene-frequencies for polydactyly in each population. The incidence in Indians with 50% Caucasian admixture suggests that the factors controlling polydactyly are in large part genetically determined. Family studies and twin studies reported elsewhere offer no clear-cut genetic model which explains the highly variable gene frequencies.
D000013:Congenital Abnormalities / Q000145:classification / Q000453:epidemiology; D005260:Female; D005385:Fingers / Q000002:abnormalities*; D006801:Humans; D007198:Indians, North American; D008297:Male; D012737:Sex Factors; D014034:Toes / Q000002:abnormalities*