In the family with complex brachydactyly and syndactyly, we detected a deletion of 21 bp in the imperfect GCN (where N denotes A, C, G, or T) triplet-containing exon 1 of HOXD13, which results in a polyalanine contraction of seven residues.
Heterozygous expansions of a polyalanine tract in HOXD13 are typically associated with synpolydactyly characterized by insertional digit duplication associated with syndactyly.
Synpolydactyly (SPD) is a dominantly inherited congenital limb malformation consisting of 3/4 syndactyly in the hands and 4/5 syndactyly in the feet, with digit duplication in the syndactylous web.
Different limb malformations due to distinct classes of HOXD13 mutations should be considered as a continuum of phenotypes and further classification of syndactyly should be done based on phenotype and genotype.
Synpolydactyly (SPD) is a rare congenital limb disorder characterized by syndactyly between the third and fourth fingers and an additional digit in the syndactylous web.