Hyperdactyly

Hyperdactyly Hyperdactyly, also known as polydactyly, is a congenital anomaly characterized by the presence of more than the usual number of fingers or toes. This condition can occur in both humans and animals and is one of the most common congenital limb malformations.

Classification

Hyperdactyly can be classified based on the location and type of extra digits:

• Preaxial polydactyly: Extra digits are located on the thumb or big toe side.
• Postaxial polydactyly: Extra digits are located on the little finger or little toe side.
• Central polydactyly: Extra digits are located between the usual digits.

Etiology

The exact cause of hyperdactyly is not fully understood, but it is believed to be a result of genetic mutations. It can occur as an isolated condition or as part of a syndrome. Some genetic syndromes associated with hyperdactyly include:

• Ellis-van Creveld syndrome
• Greig cephalopolysyndactyly syndrome
• Bardet-Biedl syndrome

Genetics

Hyperdactyly can be inherited in an autosomal dominant, autosomal recessive, or X-linked manner, depending on the underlying genetic cause. Mutations in several genes have been implicated, including:

• GLI3: Associated with Greig cephalopolysyndactyly syndrome.
• EVC and EVC2: Associated with Ellis-van Creveld syndrome.

Diagnosis

Diagnosis of hyperdactyly is primarily clinical, based on physical examination. Imaging studies such as X-rays can be used to assess the bone structure of the extra digits. Genetic testing may be performed to identify associated syndromes or specific genetic mutations.

Treatment

Treatment of hyperdactyly often involves surgical intervention to remove the extra digits, especially if they interfere with function or cause cosmetic concerns. The timing and extent of surgery depend on the individual case and the presence of any associated syndromes.

Prognosis

The prognosis for individuals with hyperdactyly is generally good, especially when the condition is isolated. Surgical correction can lead to improved function and appearance. However, the prognosis may vary if hyperdactyly is part of a more complex syndrome.

Epidemiology

Hyperdactyly occurs in approximately 1 in 500 to 1 in 1,000 live births. It is more common in certain populations and can vary in prevalence based on genetic and environmental factors.

See Also

• Syndactyly
• Brachydactyly
• Congenital limb malformations
• Jones, K. L. (1997). Smith's Recognizable Patterns of Human Malformation. Philadelphia: Saunders.
• Temtamy, S. A., & McKusick, V. A. (1978). The Genetics of Hand Malformations. Birth Defects Original Article Series.

NIH genetic and rare disease info

• NIH info on Hyperdactyly

Hyperdactyly is a rare disease.