34 year old woman with abnormal hand.

Polydactyly (or Extra Digits) is the presence of extra digits in the hand or foot. This usually affects the thumb, great toe or the little toe. These extra digits are typically incomplete and may be without bone. Polydactyly does not usually cause functional difficulties but is considered cosmetically unattractive to a sufferer. Also, extra digits of the foot frequently cause difficulty in shoe wear.

Polydactyly is usually inherited as an autosomal dominant characteristic and can usually be corrected by surgery. Also called polydactylia, polydactylism or hyperdactyly. Polydactyly can vary from an unnoticeable rudimentary finger or toe to fully developed extra digits. Polydactyly and syndactyly (fusion of the fingers or toes) can occur simultaneously when extra digits are fused. This condition is known as polysyndactyly.

The epidemiologic data on postaxial polydactyly is limited because most birth defect registries do not include them, preferring to focus on defects linked to teratogens. Despite being a common malformation, the true incidence of polydactyly is not fully known.

One study by Finley et al combined data from Jefferson County, Alabama and Uppsal County, Sweden. This study showed incidence of all types of polydactyly to be 2.3 per 1000 in white males, 0.6 per 1000 in white females, 13.5 per 1000 in black males, and 11.1 per 1000 in black females. The Swedish data alone showed polydactyly of all types to have an incidence of 1.0 per 1000, equally distributed between males and females.

While the incidence of preaxial and postaxial polydactylies has been investigated, central polydactyly has not been fully studied.

Polydactyly in the hand is not always treated, unless the sufferer wants to get rid of his or her deformity. The patient in this picture did not have it removed because her culture values it as a sign of good luck. Because Polydactyly of the foot frequently causes difficulty in shoe wear, surgery is often necessary. This operation, where the physician will simply cut and remove the extra digit, should be performed on children after 9 to 12 months of age. This makes shoe fitting no longer a problem.

Charles E. Crutchfield III, MD
Clinical Adjunct Associate Professor of Dermatology
At the
University of Minnesota Medical School
Medical Director, Crutchfield Dermatology
www.CrutchfieldDermatology.com

Informnation obtained from www. MDConsult.com and http://www.hmc.psu.edu/healthinfo/pq/poly.htm and http://www.emedicine.com/derm/topic692.htm