Thumb/hallux duplication and preaxial polydactyly type I

Abstract

It was recently shown that hand postaxial polydactyly differed from foot postaxial polydactyly. The aim of this work was to test whether thumb and hallux duplication also had different clinical and epidemiological characteristics, depending on limb involvement. We studied 920 newborn infants with first digit duplication, ascertained among 3,444,374 births by the Latin-American Collaborative Study of Congenital Malformations (ECLAMC), from 1967 to 1995. Since biphalangeal thumb duplication or hallux duplication can occur in families with triphalangeal thumb or polysyndactylous propositi, these groups were also analyzed. The 715 isolated (nonsyndromal) cases (prevalence 2.08 per 10,000) were subdivided into five groups: thumb duplication (N = 568; prevalence: 1.65/10,000); hallux duplication (N = 82; prevalence: 0.24); thumb and/or hallux duplication plus syndactyly (polysyndactyly) (N = 37; prevalence: 0.11); triphalangeal thumb (N = 24; prevalence: 0.07), and thumb duplication plus hallux duplication (N = 4; prevalence: 0.01). Both thumb and hallux duplication groups showed a significant excess of males, and right sidedness was also more frequent in both of them, though without statistical significance for hallux duplication. Thumb duplication was more often unilateral (94.7% versus hallux duplication of 81.5%), and its prevalence was higher in Bolivia (3.37/10,000) than in the other 10 Latin-American countries included (1.62/10,000). In a subseries of 405 preaxial polydactylies with matched controls, a logistic regression analysis showed that birth weight and gestational age had an effect on the calculated risk of having an infant with thumb duplication, while first trimester vaginal bleeding had only a borderline effect. None of the polydactyly groups showed abnormal values for twinning, perinatal mortality, ethnicity, maternal education, parental ages, parity, parental subfertility, or consanguinity. There were 70/405 familial cases. Their pedigrees were compatible with autosomal dominant inheritance with a 9% penetrance for thumb duplication and hallux duplication and a 70% penetrance for triphalangeal thumb and polysyndactyly. Inheritance of thumb duplication and probably the untested inheritance of hallux duplication were also compatible with a four-locus multiplicative model. The observed differences in laterality, geographical distribution, birth weight, gestational age, and first trimester vaginal bleeding between thumb duplication and hallux duplication groups suggested that apparent preaxial polydactyly type 1 is a causally heterogeneous group.

Epidemiology of isolated preaxial polydactyly type I: Data from the Polish Registry of Congenital Malformations (PRCM)

“…Therefore, our findings strongly argue for a role of environmental influence on the etiology of PPD1. Notably, the association of low birthweight with increased risk of isolated PPD1 has been reported previously [12]. …”

“…One of the largest studies of 5,171 children with a variety of digital anomalies including polydactyly, syndactyly and adactyly demonstrated that the mothers of these children were more likely to suffer from anemia, cardiac disease, lung disease, oligohydramnios, polyhydramnios, or pregnancy-associated hypertension [15]. Other implicated maternal risk factors include vaginal bleeding in the first trimester [12], and diabetes [2,15,16]. In this study, there were no PPD1 cases born to mothers with diabetes type I or II, thus it is unlikely to be an important risk factor.…”

Preaxial polydactyly of the foot

“… 2009 ). Furthermore, Orioli and Castilla ( 1999 ) showed that most cases of isolated preaxial polydactyly of the foot occur sporadically. However, in a molecular review by Johnston et al.…”

Clinical Genetics of Polydactyly: An Updated Review

“…Usually observed as unilateral form, while in bilateral cases, hands are more preferentially affected and the left hand PPD are rare as compared to right hand PPD ( Malik et al, 2014 ). There is a low occurrence of familial reappearance and high prevalence of affected males than females ( Orioli and Castilla, 1999 ). Heptadactyly or hexadactyly is also a type of thumb polydactyly in which triplication of thumb occurs, resulting in seven digits ( Zuidam et al, 2008 ).…”