crossed polysyndactyly

Crossed polysyndactyly is a congenital limb malformation disorder characterized by extra digits on the hands and feet along with abnormal fusion of parts of the toes. In affected individuals, the hands typically present with postaxial polydactyly while the feet show preaxial polydactyly accompanied by bilateral cutaneous syndactyly of the first, second, and third toes. This condition is very rare, affecting fewer than 1 in a million people. Although the precise genetic basis remains under investigation, the diagnosis is generally made based on these distinct clinical features observed at birth.

Individuals with crossed polysyndactyly usually present at birth with extra digits on one or both hands and feet. The hands often display postaxial polydactyly, whereas the feet commonly demonstrate preaxial polydactyly along with fusion of the first, second, and third toes. In some cases, skin fusion has also been reported in the hands. Not all individuals experience every feature, and the severity of the condition can vary considerably.

The underlying causes of crossed polysyndactyly are not fully understood. The precise genetic basis is still under investigation, and no specific inheritance pattern has been established to date. It is thought that a combination of genetic and developmental factors plays a role in the abnormal formation of the limbs.

Currently, management focuses on supportive care and symptom management rather than a specific drug treatment. In many cases, surgical intervention is considered to improve hand function or appearance by addressing the extra or fused digits. Treatment is tailored individually, often involving a multidisciplinary team to address functional and cosmetic concerns. Patients should discuss treatment options with their healthcare team to determine the most appropriate approach, and genetic counseling may be beneficial for families.

The long‐term outlook for individuals with crossed polysyndactyly varies, with outcomes largely dependent on the severity of the limb malformations and the interventions pursued. Many individuals achieve good functional outcomes following appropriate surgical or supportive interventions, although some may require ongoing management of residual issues. Severity and symptoms vary widely between individuals, and outcomes continue to evolve as standards of care improve. Families are encouraged to connect with specialists and genetic counselors for further guidance and support.