Merck Manual

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Finger and Toe Defects

By

Simeon A. Boyadjiev Boyd

, MD, University of California, Davis

Last full review/revision Sep 2022| Content last modified Sep 2022
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The fingers and toes may be abnormally formed, incompletely formed, or missing at birth.

Birth defects of the fingers and toes can occur while a baby is developing in the womb. For example, the baby may have too few fingers or toes. Or the baby may be born with extra fingers or toes.

In amniotic band syndrome, finger and toe defects (and other abnormalities) are caused when body parts are constricted by thin strands of tissue from the amniotic sac. The amniotic sac holds the amniotic fluid surrounding the developing fetus in the womb. The strands may tangle around the fetus, like strings or rubber bands, trapping parts of its body and restricting growth of the body part.

Polydactyly is extra fingers or toes. The little fingers or toes and thumbs or big toes are the ones most commonly duplicated. The extra finger or toe may be just a nub of fleshy tissue or the extra finger or toe could be fully functioning, having its own nerve endings, bones, and joints.

Syndactyly is webbing or fusion of fingers or toes. In syndactyly, fingers or toes do not separate, producing a weblike hand or foot. In simple syndactyly, the soft tissues are fused together. In complex syndactyly, the bones and soft tissues are fused together.

Both polydactyly and syndactyly can occur on their own or as a part of a genetic syndrome such as Apert syndrome.

Diagnosis of Finger and Toe Defects

  • Before birth, ultrasonography

  • After birth, x-rays

  • Sometimes genetic testing

After birth, doctors typically take x-rays and may do other imaging tests to determine which bones are affected.

When similar defects are present in other member's of the child's family or if doctors suspect the child has a genetic syndrome, the child may be evaluated by a geneticist. A geneticist is a doctor who specializes in genetics (the science of genes and how certain qualities or traits are passed from parents to offspring). Genetic testing of a sample of the child's blood may be done to look for chromosome and gene abnormalities. This testing can help doctors determine whether a specific genetic syndrome is the cause and rule out other causes.

Treatment of Finger and Toe Defects

  • Surgery

  • Prosthetics

Surgery can be done to separate syndactyly of the fingers or toes and improve function. Surgery may be done to remove an extra finger or toe.

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