<B>Syndactyly </B>

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Syndactyly

Etiology:

• Unknown.

Pathogenesis:

• The condition is a developmental anomaly.
• The upper limb parts appear as a outgrowth of the trunk on days 15 to 25.
• Digits appear at days 41 to 43.
• These fully separate into fingers at days 52 to 53.
• It is presumed that the formation of digits is due to apoptosis or programmed cell death between the presumptive digits.
• The pathogenesis of the condition is not completely understood, but research focuses on the role of retinoids and the homeobox (HOX) genes in giving rise to this condition by altering the apoptotic events in the primitive limb.

Epidemiology:

• Male:Female ratio is 1:1.
• Approximately 1 in 3,000 live births in the U.S. manifest syndactyly.

General Gross Description:

• Based on associated findings and anatomical features, Temtamy and McKusick have divided syndactyly into five groups.
• The most common form involves fusion of the third and fourth digits of the hands.
• Other, more extensive defects may result in the entire hand appearing as a cup with no fingers.
• In some forms, fusion of toes, especially second and third, is an associated finding.
• In other forms, is associated with polydactlyly.

General Microscopic Description:

• There appears to be relatively little, if any, description of the specific histology of syndactyly.

Clinical Correlations:

• Usually autosomal dominant.
• The lesion is obviously manifest and detected at birth.

References:
•There is no satisfactory description of syndactyly in most textbooks. •A good reference to the clinical features and embryology of syndactyly can be found in Winter and Tickle (Europeon Journal of Human Genetics, volume 1, pages 96-104, 1993).