Having extra fingers or toes (6 or more) can occur on its own. There may not be any other symptoms or disease present. Polydactyly may be passed down in families. This trait involves only one gene that can cause several variations.

African Americans, more than other ethnic groups, can inherit a 6th finger. In most cases, this is not caused by a genetic disease.

Polydactyly can also occur with some genetic diseases.

Extra digits may be poorly developed and attached by a small stalk. This most often occurs on the little finger side of the hand. Poorly formed digits are usually removed. Simply tying a tight string around the stalk can cause it to fall off in time if there are no bones in the digit.

In some cases, the extra digits may be well-formed and can even function.

Larger digits may need surgery to be removed.

Causes may include:

• Asphyxiating thoracic dystrophy
• Carpenter syndrome
• Ellis-van Creveld syndrome (chondroectodermal dysplasia)
• Familial polydactyly
• Laurence-Moon-Biedl syndrome
• Rubinstein-Taybi syndrome
• Smith-Lemli-Opitz syndrome
• Trisomy 13

You may need to take steps at home after surgery to remove an extra digit. These steps may include checking the area to make sure the area is healing and changing the dressing.

Most of the time, this condition is discovered at birth when the baby is still in the hospital.

The health care provider will diagnose the condition based on a family history, medical history, and a physical exam.

Medical history questions may include:

• Have any other family members been born with extra fingers or toes?
• Is there a known family history of any of the disorders linked to polydactyly?
• Are there any other symptoms or problems?

Tests used to diagnose the condition:

• Chromosome studies
• Enzyme tests
• X-rays
• Metabolic studies

You may want to make a note of this condition in your personal medical record.

Extra digits may be discovered after the first 3 months of pregnancy with ultrasound or a more advanced test called embryofetoscopy.

Extra digits; Supernumerary digits

Carrigan RB. The upper limb. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 701.

Mauck BM. Congenital anomalies of the hand. In: Azar FM, Beaty JH, eds. Campbell's Operative Orthopaedics. 14th ed. Philadelphia, PA: Elsevier; 2021:chap 80.

Son-Hing JP, Thompson GH. Congenital abnormalities of the upper and lower extremities and spine. In: Martin RJ, Fanaroff AA, Walsh MC, eds. Fanaroff and Martin's Neonatal-Perinatal Medicine. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 99.

Updated by: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.