Triphalangeal Thumb-Polysyndactyly Syndrome

Triphalangeal thumb-polysyndactyly syndrome (TPT-PS) is a hand-foot malformation characterized by triphalangeal thumbs and pre- and postaxial polydactyly, isolated syndactyly or complex polysyndactyly.

Epidemiology

It has been described in some large pedigrees.

Clinical description

Clinical presentation is variable within families, ranging from mild to severe. Malformations of the feet are usually less severe than those of the hands.

Etiology

TPT-PS is caused by duplication encompassing the limb-specific regulatory element (ZRS) of sonic hedgehog SHH, which lies in intron 5 of the `limb region 1 homolog' gene, LMBR1 (7q36).

Genetic counseling

This syndrome is transmitted in an autosomal dominant manner with complete penetrance and variable expression.