Clinical and phenotypic variability in polydactyly families ascertained from Rawalpindi-Islamabad, Pakistan.

Abstract

Polydactyly is a congenital limb defect in whi ch an extra fi nger or toe is present in the hands or feet, respectivel y. Polydactyly is the most frequently observed hereditary limb/digit anomaly. It may appear as an isolated anomaly or a pal1 of syndromes. Isolated polydactyly mainl y has autosomal dominant mode of inheritance while syndromic polydactylies commonl y segregate autosomal recessively. There is a lack of knowl edge about the phenotypic spectrum of polydactyly in the Pakistan i population. In order to partially fill this information gap the present study was undertaken . During Nov. 20 II to Sep. 20 12, field visits were launched at Districts Rawalpind i and Islamabad and families with limb defects were recruited. Twenty families of polydactyly were ascertained but only 17 were included in this study. Sixteen famil ies were depicting non-syndromi c polydactyly and one was syndromic, i.e., Ellis-van Creveld syndrome. In the nonsyndromic polydactyly cases, there were eleven sporadic and five fami li al. There were ten preaxial polydact Iy and six postaxial polydactyly cases. A broad spectrum of polydactyly phenotype was observed in the recruited families. The most common phenotype was preaxial polydactyly. Different phenotypic manifestation of extra digit was observed, i.e., partia ll y developed to full y develop which were classified according to standard criteria. Among the sporadic cases, there was a preponderance of affected females. The mode of inheritance of sporadic cases cannot be inferred and it was assumed that they may originate due to novel mutations or stochastic factors. In the familial cases, mal e were more commonly affected and autosomal recessive and X-li nked recessive modes of inheritance were observed . This study is an effort to appreciate the clin ical spectrum of one of the most common limb anomaly in the Rawalpindi/Islamabad population. This study witnessed a broad phenotypic variability of polydactyly. This information would help in further delineation of sub-types of polydactyly which would be highl y beneficia l for the affected subj ects and the ir fam ili es in terms of genetic counseling and management.