Adoptive Families Association of BC
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Syndactylism is when the fingers or toes of an individual are fused together. This can include multiple digits and has various degrees of depth. The fusion can be only skin deep or go as deep as connected bones, blood vessels, and nerves. 

It is a congenital condition which the child is born with. It could be a genetic inherited trait or the result of a variety of rare genetic disorders. 

Treatment usually involves surgically separating the fused digits. Depending on the extent of connective tissue the surgery can become more difficult but has a great success rate for most patients. A skin graft from another area of the body may be needed to cover the newly exposed digits.

Syndactyl children can have polydactylism as well, the presence of more than five fingers or toes on each hand or foot.