Definiton: Syndactyly is an abnormal connection between adjacent digits. It is described according to the magnitude and extent of the linkage. The fusion involves only soft tissues (simple) or includes bone (complex). Syndactyly is either complete, along the entire length of the finger or spares the distal part (incomplete). It links two digits (2 and 3 being the more frequent), the four last digits or all the fingers (such as in Apert syndrome). Syndactyly is relatively common (2-3/10000 live births). The anomaly can be sporadic, familial, or coexist with anomalies.

Etiology

 isolated syndactyly (non-syndromal syndactyly)

• familial syndactyly affects usually the second and third digits and is not associated with other conditions. The transmission is autosomal dominant with variable expressivity and incomplete penetrance.

 syndromal syndactyly

• Poland syndrome (symbrachydactyly with pectoralis muscle defect) (Poland sequence)
• acrocephalosyndactylies (syndactyly with craniosynostoses)
  • Apert syndrome
  • Saethre-Chotzen syndrome
  • Pfeiffer syndrome
  • Summit syndrome
  • Hermann-Opitz syndrome
  • Waardenburg syndrome

• craniodigital syndrome with mental retardation
• oculodentodigital dysplasia
• otopalatodigital syndrome type 2 (OPD2)
• cryptophtalmus syndrome (Fraser syndrome)
• ABS syndrome (acrosyndactyly/amputation)
• triploidy

 constriction bands

Variants

 polysyndactyly
 acrosyndactyly