Which polydactyly type is least common?

• A. Preaxial polydactyly
• B. Central polydactyly
• C. Postaxial polydactyly
• D. Mesaxial polydactyly

Answer: (B)

Understanding where extra digits appear in polydactyly helps explain why some forms are rarer than others. The limb’s development patterns along the anterior-posterior axis tend to produce duplications at the ends of the hand—the postaxial (ulnar/little-finger side) region is the most common, and preaxial (radial/thumb side) duplications are also seen with some frequency, especially in certain populations. Central polydactyly, which involves duplications in the middle part of the hand, requires a much more unusual disruption of limb patterning in the central digits. This kind of midline, central disturbance is less likely to occur in isolation and is often associated with broader or syndromic limb anomalies, making it far less common than the other forms.