Introduction:
Polydactyly is a medical condition where the child is born with one or more fingers on both hands or toes. The word polydactyly consists of poly which means many, and dactylos means digits. The alternate name of polydactyly is hyperdactyly, supernumerary digit. The extra fingers on the hand and foot describe it as supernumerary(more than a normal number).
Polydactyly is the most common congenital anomaly of the hand and foot, which is characterized by extra fingers in the hand and foot due to developmental defects during anterior-posterior patterning of the limb. It usually appears isolated, which is non-syndromic polydactyly, associated with various congenital disabilities syndromic polydactyly. The physician should carefully evaluate the child with polydactyly if there are any associated systemic syndromic conditions. Polydactyly is mostly seen on the right hand rather than on the left hand, upper limb rather than the lower limb, and on the left foot rather than the right foot. Polydactyly of hands or feet may or may not contain bone. It is more common in black infants than in white infants and most frequently affects male children than female children. Polydactyly is a common condition that often occurs genetically in families.
Where Can the Extra Fingers Be Located?
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The extra fingers are usually smaller than the normal fingers.
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The extra fingers in the polydactyly can be located on the little finger side, thumb finger side, and in the middle of the hand. It is found in the same locations on the feet as on the hands.
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Polydactyly on the little finger side is more common, whereas on the thumb finger side and in the middle of the hand is less common.
How Do Extra Fingers Appear?
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It appears as a raised lump of soft tissue. It does not contain bones. This appearance of an extra finger may be called nubbin.
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It appears as partially formed fingers or toes. It may contain some bones but not joints.
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It appears as fully formed fingers or toes like normal fingers. It contains bones and joints.
How Is Polydactyly Classified?
Polydactyly can be classified into three major categories. First, they are preaxial, central, and postaxial. Later, the preaxial and postaxial can be said to be Radial and Ulnar polydactyly.
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Preaxial or Radial Polydactyly: This type of polydactyly is rare. The extra fingers are found on the outside of the thumb. The side of the hand is known as the radial side. If the extra finger is on the big toe, it is called a tibial polydactyly.
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Central Polydactyly: Central polydactyly is a rare type. The extra finger is attached to the middle, ring, or index finger. It is often attached to the index finger.
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Postaxial or Ulnar Polydactyly: Ulnar polydactyly is the most common type. The extra fingers are found outside the little finger. This side of the hand is known as the ulnar side. This condition in the toe is called fibular polydactyly.
What Causes Polydactyly?
Polydactyly is a genetic condition. It runs in families. Thus this type is said to be familial polydactyly. Familial polydactyly comes under isolated polydactyly, meaning patients do not associate with other syndromes. The other cause of polydactyly is that it is associated with various syndromes. Patients with such syndromes may be found with extra fingers.
The associated syndromes are:
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Syndactyly (webbed hands or feet).
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Trisomy 13 (severe chromosomal condition).
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Carpenter syndrome (abnormalities in skull, toes, and fingers).
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Asphyxiating thoracic dystrophy (inherited bone growth disorder).
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Meckel syndrome (a genetic condition).
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Down syndrome (a genetic disorder).
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Basal cell nevus syndrome (inherited disorder with certain facial and skeletal abnormalities).
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Fanconi anemia (hemoglobin disorder).
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Mohr syndrome (an autosomal recessive inherited disease).
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Oro- facial- digital syndrome (disorder associated with varied inheritance patterns).
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Ellis van Creveld syndrome (a genetic disorder).
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Acro callosal syndrome (a rare brain abnormality).
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Mirror hand deformity (symmetric duplication of upper limb).
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Laurence- moon- Biedl syndrome (autosomal recessive disorder).
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Rubinstein- Taybi syndrome (a condition with short stature and distinctive facial features).
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Smith- Lemli- Opitz syndrome (a developmental disorder).
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Pallister- Hall syndrome (a spectrum of anomalies).
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Short rib polydactyly.
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Biemond syndrome (a neurological condition).
How Is Polydactyly Diagnosed?
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X-ray imaging is used to diagnose polydactyly, thus, affected bone structures on hands and feet are observed.
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The physicians may diagnose this by asking about the patient's medical history and family history.
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Polydactyly can also be diagnosed using tests like chromosomal, enzyme, and metabolic studies.
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Sometimes polydactyly is diagnosed in the first trimester of pregnancy using an ultrasound scan of the uterus or embryo fetoscopy. Thus this diagnosis is helpful for physicians to provide treatment for polydactyly and other associated syndromes.
How Is Polydactyly Treated?
The treatment of polydactyly depends on its type. The treatment varies for all three types, they are:
Treatment for Little Finger Duplication: In most cases, little finger duplication does not require any treatment, as it affects hand function. Some patients require treatment for cosmetic reasons.
If an extra little finger is formed only by soft tissues and not bone, this finger is removed by tying a tight string around the finger. Thus it cuts off the blood supply, and the soft tissue disappears. This procedure is done after one year of the baby being born.
If an extra little finger is fully formed with bone and if it functions, surgery is required for its removal. Consultation with a specialized surgeon is required before surgery due to its functional importance.
Treatment for Thumb Duplication: The treatments for thumb duplication are quite complicated as the extra thumb affects the functions of the other thumb. During surgical removal, the functional thumb should undergo reconstructive techniques.
Treatment for Central Polydactyly: The treatment for central polydactyly is that the surgery is done by removing tendons and ligaments by keeping the other finger intact.
It is also treated by removing the extra finger and reconstructing the finger to which it is attached.
Conclusion:
The prognosis for isolated polydactyly is excellent, whereas the prognosis for polydactyly associated with syndromes depends on its severity. Thus babies with polydactyly should be treated carefully. In addition, parents are advised to reach out to the physician if they find their children with more than five fingers on their hands or feet.
