Polysyndactyly is a congenital anomaly, combining polydactyly and syndactyly, in which affected individuals have an extra finger or toe that is connected, via fusing or webbing, to an adjacent digit.

Primarily, mutations are found in the zone of polarizing activity regulatory sequence, or ZRS, that controls the expression of SHH in developing limbs.

These genomic regions regulate proliferation and differentiation in the limb bud, and can lead to phenotypic anomalies, including polysyndactyly, if mutated.

[5][7] Treatment is generally aimed at normalizing both function and appearance of the affected extremity[3] and, in the case of polysyndactyly of the foot, shoe fit and comfort.

If there are no comorbid or underlying genetic conditions, surgical removal of the extra digit generally results in a high quality of life.

Parents of children with polysyndactyly have reported high physical, social, emotional, and school functioning and good psychosocial health after removal of the extra digit.