Syndactyly is a congenital condition, resulting from a failure of fingers to separate into individual appendages during embryonic development. The condition is therefore, characterized by webbing of the toes and/or fingers. At least five different classes of syndactyly have been identified, of which syndactyly I is the most common. The webbing seen in syndactyly I usually is simple, involving only a skin connection between the fingers, but may also sometimes be complex, involving fusion of the distal phalanges. The most commonly affected are the 3rd and 4th fingers.
Syndactyly may also be present as a part of other syndromes like Apert Syndrome, Carpenter's Syndrome, Smith-Lemli-Opitz Syndrome, Pfeiffer Syndrome, or Cornelia de Lange Syndrome. Therefore, presence of syndactyly may have to be followed up by chromosome studies, enzyme assays, metabolic studies, and other diagnostic methods to identify the presence of any syndrome.
Syndactyly type 1 is inherited in an autosomal dominant manner. It is clinically heterogeneous with at least four different subtypes and is caused by duplications on chromosome 2q35.