How does polydactyly occur during limb development?

Polydactyly is a congenital anomaly characterized by the presence of extra digits on the hands or feet. During normal limb development, the tips of limb buds flatten into hand or foot plates, which then undergo indentation to form the distinct rudiments of the digits.123

Polydactyly occurs when this developmental process is disrupted, often due to the inheritance of an abnormal gene that causes a localized disturbance in the growth process of the embryo. While the exact cellular mechanisms can vary, these genetic factors interfere with the normal patterning or segmentation of the digit rudiments within the limb plate. In some instances, polydactyly is an isolated anomaly, while in others, it serves as a symptom of broader genetic syndromes, such as trisomy 13 or Ellis–van Crevald syndrome.21