Zygodactyly 1

Description

Syndactyly type I (185900) is an autosomal dominant limb malformation characterized in its classical form by complete or partial webbing between the third and fourth fingers and/or the second and third toes. Zygodactyly is a subtype of type I syndactyly in which webbing of second and third toes occurs without hand involvement (summary by Malik et al., 2005).

Clinical Features

Malik et al. (2005) described a large consanguineous Pakistani family with autosomal inheritance of bilateral webbing of second and third toes without hand involvement. Four individuals showed complete soft tissue syndactyly including partial fusion of nails; 4 showed partial cutaneous syndactyly; and 4 showed mild unilateral syndactyly, with the other foot being either normal or with superficial fusion of involved toes. They described a similar phenotype in a nonconsanguineous German family. Malik et al. (2005) used the term zygodactyly as a synonym for cutaneous webbing of the second/third toe.

Mapping

In the Pakistani family with zygodactyly, Malik et al. (2005) performed a genomewide screen, which obtained evidence of linkage with marker D3S2409 on chromosome 3p21.31 (lod = 3.38; theta = 0.00). Malik et al. (2005) designated the 3p21.31 locus ZD1 (zygodactyly 1). This locus was clearly excluded in the German family with similar phenotype described by them.

Nomenclature

In the classification of type I syndactyly of Malik et al. (2005), the ZD1 locus represents subtype 1, which is characterized by cutaneous webbing of the second and third toes without hand involvement and is the mildest and most common form. The phenotype varies from unilateral minor impression of webbing to bilateral complete webbing of second and third toes including a fusion of nails. Bony involvement is never observed. This autosomal dominant subtype was originally designated zygodactyly (e.g., Weidenreich, 1924, Penrose, 1946), although it later became accepted to use the term zygodactyly for type I syndactyly in general. The locus on 2q34-q36 described in entry 185900 represents subtype 2, characterized by bilateral cutaneous and/or bony webbing of third and fourth fingers and of second and third toes. Also see Malik et al. (2005).