Polydactyly and syndactyly

Definition

Polydactyly and syndactyly are congenital malformations of the fingers and/or toes. Polydactyly is the presence of extra fingers or toes, and syndactyly is the fusing together or webbing of two or more fingers or toes.

Description

Polydactyly and syndactyly can vary in the degree of severity. Polydactyly may range from small skin tags on the side of the hands to fully formed extra fingers with bone, blood vessels, and muscle tissue. Polydactyly is classified as postaxial if the extra digit is located beside the little finger or preaxial if the extra digit is located near the thumb. Syndactyly may be either a complete fusion of fingers or toes or a looser webbing of skin between them. Syndactyly and polydactyly may occur simultaneously when extra digits are fused in a condition known as polysyndactyly. Polydactyly and syndactyly are usually isolated conditions, meaning the child will have no other birth defects; however, both are also found in many complex and sometimes lethal groups of anomalies or syndromes.

Demographics

Syndactyly of the fingers is the most common malformation affecting the hand. It occurs in approximately one in 2,000 live births. Postaxial polydactyly, or an extra pinky finger, is the second most common malformation of the hand, occurring in approximately one in 3,000 births. Polydactyly of the toes, especially of the little toe, is also a common malformation, occurring in approximately two in 1,000 births. Thirty percent of all children with polydactyly have family members with some type of polydactyly, and it is more common in African Americans. Syndactyly is an equally common malformation and runs in families as well.

Causes and symptoms

Polydactyly and syndactyly are conditions that occur in the developing fetus. Most often these conditions are caused by genetic factors. Both polydactyly and syndactyly can be caused by the presence of an autosomal dominant trait. An autosomal dominant trait is a gene that is not related to the chromosome that determines gender; therefore, it affects boys and girls equally. Because the gene is dominant, when one parent has the gene, each of his or her children has a 50 percent chance of having polydactyly or syndactyly.

The primary symptom of polydactyly is the presence of extra digits on the hands or feet. Polydactyly rarely causes any difficulties for the child. The extra fingers and/or toes are usually removed for cosmetic reasons. In children with syndactyly of the hand, finger function may be impaired and, in cases where fingers of different lengths are connected by tissue, finger growth may be limited unless surgery to separate the fingers is performed.

Diagnosis

Diagnosis is made during the initial physical examination at birth. Some children with polydactyly will need radiographs or x rays to determine if there is bone present in the extra digit. This will indicate what type of surgery is necessary to remove the extra finger or toe. When polydactyly is more severe and involves digits with bone, a pediatric orthopedic surgeon will perform the repair. In children with syndactyly, the surgeon must determine if the fusion involves muscle tissue and blood vessels, and in children with severe polydactyly of the fingers, a surgeon specializing in hands may evaluate the child as well. Some children with syndactyly may also have cardiac or heart problems; therefore, an electrocardiogram (EKG) may be ordered to evaluate heart function.

Treatment

For children with minor cases of polydactyly, the extra finger or toe may be tied at its base to restrict blood flow into it. Eventually the extra digit will fall off. In more significant cases, a pediatric orthopedic surgeon will remove the extra finger or toe and reconstruct the part of the hand or foot that was affected. The surgeon will save the digit that best fits with the others. This surgery usually occurs when the child is between one and two years old.

Prognosis

For children with isolated polydactyly and syndactyly, the prognosis is excellent. After surgery most children will have full use of their fingers and toes. In children with syndromes and additional birth defects, the prognosis may be poor; however, the problems these children may experience will not be related to polydactyly or syndactyly, but rather to the sometimes lethal conditions that accompany the other defects present.

Prevention

There is no known prevention for polydactyly and syndactyly.

Parental concerns

Parents may be concerned about their child's ability to use his hands and feet. For most children, surgery corrects the condition and allows normal use of the hands and feet. Parents may also be concerned about the appearance of the hands and feet. In most cases, following surgery, they will have a normal appearance.

Children with more severe polydactyly and syndactyly will have surgery to correct the malformation. These children will need to be prepared for the experience. Polydactyly and syndactyly correction surgery is usually performed when the child is between the ages of one and two years. When talking to children of this age, tone of voice is as important as the words used. Using a calm and comforting voice and simple language, parents can tell the child what will happen. Young children should be told the day before surgery that they will be going to the hospital. Parents may want to use dolls or stuffed animals to show their child where the doctor will work. If a child must spend the night, it is helpful to bring a toy or familiar object to make the child feel more comfortable in the hospital. Afterwards, the child may reenact the experience during play or in drawings . Parents should be prepared to talk and play with their child in this way.

When to call the doctor

Following surgery, parents should call the doctor if any of these symptoms occur:

• Unexpected bleeding from the wound
• An oral temperature of over 101 degrees
• Pain that is nor relieved by pain medication
• A persistent dry cough
• Nausea or vomiting that does not improve
• Redness or swelling around the incision site

KEY TERMS

Autosomal dominant trait —One of the non-X or non-Y chromosomes that will always express itself when present.

Congenital —Present at birth.

Electrocardiagram (ECG, EKG) —A record of the electrical activity of the heart, with each wave being labeled as P, Q, R, S, and T waves. It is often used in the diagnosis of cases of abnormal cardiac rhythm and myocardial damage.

Gene —A building block of inheritance, which contains the instructions for the production of a particular protein, and is made up of a molecular sequence found on a section of DNA. Each gene is found on a precise location on a chromosome.

Malformation —An irregular or abnormal formation or structure.

Postaxial —Situated behind or away from the axis or midline of the body.

Preaxial —Situated in front of the axis or midline of the body.

Radiograph —The actual picture or film produced by an x-ray study.

Syndrome —A group of signs and symptoms that collectively characterize a disease or disorder.

Webbing —A tissue or membrane that connects two digits at their base or for the greater part of their length.

Resources

BOOKS

Behrman, Richard E., Robert M. Kliegman, and Hal B. Jenson, editors. Nelson Textbook of Pediatrics. 16th ed. Philadelphia: W.B. Saunders Company, 2000.

Friedman, William F., and John S. Child. "Congenital Heart Disease in the Adult." In Harrison's Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1997.

Rudolph, Colin D., and Abraham M. Rudolph, editors. Rudolph's Pediatrics. 21st ed. New York: McGraw-Hill, 2003.

WEB SITES

Somerset Medical Center, "Pediatric Same Day Surgery," Somerset Medical Center, Somerville, NJ, <www.somersetmedicalcenter.com/body.cfm?id=380> (accessed August 11, 2004).

Deborah L. Nurmi,, MS

Polydactyly and Syndactyly

Definition

Polydactyly and syndactyly are congenital irregularities of the hands and feet. Polydactyly is the occurrence of extra fingers or toes, and syndactyly is the webbing or fusing together of two or more fingers or toes.

Description

Polydactyly can vary from an unnoticeable rudimentary finger or toe to fully developed extra digits.

Syndactyly also exhibits a large degree of variation. Digits can be partially fused or fused along their entire length. The fusion can be simple with the digits connected only by skin, or it can be complicated with shared bones, nerves, vessels, or nails.

Polydactyly and syndactyly can occur simultaneously when extra digits are fused. This condition is known as polysyndactyly.

Causes and symptoms

Polydactyly and syndactyly are due to errors in the process of fetal development. For example, syndactyly results from the failure of the programmed cell death that normally occurs between digits. Most often these errors are due to genetic defects.

Polydactyly and syndactyly can both occur by themselves as isolated conditions or in conjunction with other symptoms as one aspect of a multi-symptom disease. There are several forms of isolated syndactyly and several forms of isolated polydactyly; each of these, where the genetics is understood, is caused by an autosomal dominant gene. This means that since the gene is autosomal (not sex-linked), males and females are equally likely to inherit the trait. This also means that since the gene is dominant, children who have only one parent with the trait have a 50% chance of inheriting it. However, people in the same family carrying the same gene can have different degrees of polydactyly or syndactyly.

Polydactyly and syndactyly are also possible outcomes of a large number of rare inherited and developmental disorders. One or both of them can be present in over 100 different disorders where they are minor features compared to other characteristics of these diseases.

For example, polydactyly is a characteristic of Meckel syndrome and Laurence-Moon-Biedl syndrome. Polydactyly may also be present in Patau's syndrome, asphyxiating thoracic dystrophy, hereditary spherocytic hemolytic anemia, Moebius syndrome, VACTERL association, and Klippel-Trenaunay syndrome.

Syndactyly is a characteristic of Apert syndrome, Poland syndrome, Jarcho-Levin syndrome, oral-facial-digital syndrome, Pfeiffer syndrome, and Edwards syndrome. Syndactyly may also occur with Gordon syndrome, Fraser syndrome, Greig cephalopolysyndactyly, phenylketonuria, Saethre-Chotzen syndrome, Russell-Silver syndrome, and triploidy.

In some isolated cases of polydactyly or syndactyly, it is not possible to determine the cause. Some of these cases might nevertheless be due to genetic defects; sometimes there is too little information to demonstrate a genetic cause. Some cases might be due to external factors like exposure to toxins or womb anomalies.

Diagnosis

Polydactyly and syndactyly can be diagnosed by external observation, x ray, and fetal sonogram.

Treatment

Polydactyly can be corrected by surgical removal of the extra digit or partial digit. Syndactyly can also be corrected surgically, usually with the addition of a skin graft from the groin.

Prognosis

The prognosis for isolated polydactyly and syndactyly is excellent. When polydactyly or syndactyly are part of a larger condition, the prognosis depends on the condition. Many of these conditions are quite serious, and early death may be the probable outcome.

Prevention

There is no known prevention for these conditions.

Resources

ORGANIZATIONS

March of Dimes Birth Defects Foundation. 1275 Mamaroneck Ave., White Plains, NY 10605. (914) 428-7100. [email protected]. 〈http://www.modimes.org〉.

National Institute of Child Health and Human Development. Bldg 31, Room 2A32, MSC 2425, 31 Center Drive, Bethesda, MD 20892-2425. (800) 505-2742. 〈http://www.nichd.nih.gov/sids/sids.htm〉.

OTHER

OMIM Home Page, Online Mendelian Inheritance in Man. 〈http://www.ncbi.nlm.nih.gov/Omim〉.

KEY TERMS

Autosomal chromosome— One of the non-X or non-Y chromosomes.

Congenital— A condition present at birth.

Digit— A finger or a toe.

Dominant trait— A genetic trait that will always express itself when present as one of a pair of genes (as opposed to a recessive trait where two copies of the gene are necessary to give the individual the trait).

Gene— A portion of a DNA molecule that either codes for a protein or RNA molecule or has a regulatory function.

Triploidy— The condition where an individual has three entire sets of chromosomes instead of the usual two.

Trisomy— An abnormal condition where three copies of one chromosome are present in the cells of an individual's body instead of two, the normal number.