title: Hand and foot postaxial polydactyly: two different traits.
abstract: The aim of this work was to test whether postaxial hexadactyly had different clinical and epidemiological characteristics depending on hand or foot involvement. In the period 1967-1993, the Latin-American Collaborative Study of Congenital Malformations (ECLAMC) enrolled 1,582,289 births, and 2,271 cases with isolated (nonsyndromal) postaxial polydactyly (5th-digit hexadactyly). The prevalence was 14.3/10,000 births. Postaxial polydactyly (PP) of the hand (HPP) was the most frequent type (N:1,733; 76.3%; prevalence: 11.0/10,000), followed by foot PP (FPP=N:351; 15.5%; prevalence: 2.2), and hand and foot PP (BPP=N:187; 8.2%; prevalence: 1.2). Unlike HPP (55.0% bilateral; 77.2% left), FPP was less frequently bilateral (19.4%), with lower preference for the left side (55.5%). As expected, HPP was associated with African Black ethnicity, male sex, twinning, low maternal education, parental consanguinity, and there was frequent recurrence in 1st-degree relatives. Conversely, FPP was associated with Amerindian racial background, parental subfertility, and bleeding in the 1st trimester of pregnancy. BPP displayed the highest frequency of associated congenital defects (23.4%, vs HPP:6.6%, FPP: 15.4%). In its isolated form, BPP resembled HPP more than FPP with respect to left preference (90.9%), familial recurrence (11.0% of 1st degree relatives), and low maternal education. Although male sex preference and high frequency of twinning was observed in the 3 PP subtypes, statistical significance was present only in HPP. None of the 3 PP subtypes showed abnormal values for perinatal mortality, birth weight, length of gestation, parental ages, or parity. A logistic regression analysis showed Black race only to be associated with HPP, parental subfertility with FPP, parental consanguinity with BPP, and non-Black race with both FPP and BPP. The data presented here are the first indication that HPP and FPP are 2 different entities, with a larger genetic component in HPP than in FPP.
authors.affiliation: ECLAMC (Latin-American Collaborative Study of Congenital Malformations, WHO Collaborating Centre for the Prevention of Birth Defects) at Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil.
authors.forename: E E
authors.initials: EE
authors.lastname: Castilla
authors.forename: M
authors.initials: M
authors.lastname: da Graca Dutra
authors.forename: R
authors.initials: R
authors.lastname: Lugarinho da Fonseca
authors.forename: J E
authors.initials: JE
authors.lastname: Paz
mesh_terms: D005006:Ethnicity / Q000235:genetics; D005260:Female; D005532:Foot Deformities, Congenital / Q000453:epidemiology* / Q000208:ethnology; D006228:Hand Deformities, Congenital / Q000453:epidemiology* / Q000208:ethnology; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D010641:Phenotype; D017689:Polydactyly / Q000453:epidemiology* / Q000208:ethnology; D011247:Pregnancy; D015995:Prevalence; D012727:Sex Characteristics