Prevalence:

• 1 in 3,000 births.

Ultrasound diagnosis:

• Two or more digits (bone or soft tissue) are fused together.

Associated abnormalities:

• Chromosomal abnormalities: common finding in triploidy.
• In most cases it is an isolated finding, but there is a common association with genetic syndromes:
  • Apert syndrome: autosomal dominant; brachysyndactyly of hands and feet, craniosynostosis, hypertelorism, heart defects.
  • Carpenter syndrome: autosomal recessive; polysyndactyly, craniosynostosis.
  • Fraser syndrome: autosomal recessive; microphthalmia, facial cleft, tracheal atresia, bilateral renal agenesis, heart defects, syndactyly or polydactyly.

Investigations:

• Detailed ultrasound examination.

Follow up:

• Follow-up should be standard.

Delivery:

• Standard obstetric care and delivery.

Prognosis:

• Isolated cases: good prognosis.

Recurrence:

• Isolated familial polysyndactyly: 50%.
• Part of Apert syndrome: 50%.
• Part of Carpenter and Fraser syndrome: 25%.
• Part of triploidy: no increased risk.