polydactyly

Polydactyly is a congenital condition characterized by the presence of more than five fingers on a hand or more than five toes on a foot. It can involve extra digits at the preaxial (thumb or big toe side), postaxial (little finger or little toe side), or central portion of the limb. Isolated polydactyly occurs without other anomalies, while syndromic polydactyly is associated with genetic syndromes or additional congenital conditions.

Most cases are sporadic, but some are inherited in autosomal dominant or autosomal recessive patterns. Genetic factors implicated include mutations or regulatory changes in limb development pathways, notably SHH signaling and GLI3, among others. Central polydactyly is often part of a detectable syndrome; preaxial and postaxial forms may run in families.

Diagnosis is clinical and supported by plain radiographs to determine the extra bone, joints, and its relation to the normal digits. Ultrasound or genetic testing may be offered when a syndromic cause is suspected or for family planning.

Treatment aims to improve function and appearance and is usually surgical. The timing and type of surgery depend on the digit’s size, position, and function; many cases are repaired or removed in infancy or early childhood, with reconstruction as needed. Isolated postaxial polydactyly generally has a favorable outcome after surgery; central and syndromic forms require multidisciplinary care.

Epidemiology varies by population; polydactyly affects roughly 1 in several hundred to a thousand live births. Prognosis depends on associated conditions and the complexity of the anomaly.