Type II familial synpolydactyly: report on two families with an emphasis on variations of expression

Type II familial synpolydactyly is rare and is known to have variable expression. However, no previous papers have attempted to review these variations. The aim of this paper was to review these variations and show several of these variable expressions in two families. The classic features of type II familial synpolydactyly are bilateral synpolydactyly of the third web spaces of the hands and bilateral synpolydactyly of the fourth web spaces of the feet. Several members of the two families reported in this paper showed the following variations: the third web spaces of the hands showing syndactyly without the polydactyly, normal feet, concurrent polydactyly of the little finger, concurrent clinodactyly of the little finger and the ‘homozygous' phenotype. It was concluded that variable expressions of type II familial synpolydactyly are common and awareness of such variations is important to clinicians.