Four-generation postaxial polydactyly in a Chinese family

Abstract

Polydactyly, one of the fairly common congenital deformities of the hands and/or feet, occurs as an isolated disorder or as part of a syndrome. It is not only observed sporadically, but also inherited with a mainly autosomal dominant inheritance. However, postaxial polydactyly in both hands and feet with 24 digits in total was rarely reported in China. CASE REPORT We present a Chinese family with affected members in four generations. The family members were inhabitants in the west of Zhejiang Province, China. They had not got consanguineously married. The proband (IV5) was found on a routine physical examination. Among 38 subjects in four generations of the family there were 10 affected men and 9 affected women (Fig. 1). They all had bilateral postaxial polydactyly with duplications of the fifth digit in hands and feet (Fig. 2). The affected members were examined carefully to exclude other congenital deformities.Fig. 1.: The pedigree of the family: square and round symbols indicating the male and female members, respectively. The black-shaded figures indicating family members with 24 digits.Fig. 2.: Bilateral postaxial polydactyly with duplications of the fifth digit in hands and feet.DISCUSSION Polydactyly can be generally subclassified into preaxial and postaxial forms according to its anatomical location.1 Most cases of polydactyly of the hand and foot were postaxial, and preaxial involvement was uncommon.2 Postaxial polydactyly is characterized by duplications of the fifth digit in hands and/or feet. Two phenotypes have been reported so far. The extra digit is well formed and articulates with the fifth or extra metacarpal bone in type A, whereas the rudimentary extra fifth digit is presented in type B.3 The etiology of polydactyly can be classified into environmental and genetic. Congenital hand malformations including polydactyly are mostly single gene diseases.4 Mutations in the GLI3 gene are associated with postaxial polydactyly in a single family5 and other loci for this disease have been identified on chromosome 7q21-q34 and chromosome 19p13.1–13.2.3,6 Most inherited cases of polydactyly involving the hand and foot are of autosomal dominant inheritance but still a few syndromic postaxial cases (Ellis-van Creveld syndrome), are of autosomal recessive inheritance.2 In this report, the pedigree of the family shows the affected familial members of each generation, almost equal numbers of affected males and females, and the marriages between affected and normal subjects producing affected and normal progeny, clearly indicating an autosomal dominant mode of inheritance in postaxial polydactyly. In principle, the extra digit is removed for the treatment of postaxial polydactyly. The surgery should be performed when the patient is young.