Non-syndromic polydactyly

Non-syndromic polydactyly is a congenital limb malformation characterized by the presence of extra fingers and/or toes (supernumerary digits) that occurs as an isolated finding without other associated anomalies or systemic involvement. Unlike syndromic forms of polydactyly, which occur as part of broader genetic syndromes affecting multiple organ systems, non-syndromic polydactyly affects only the hands and/or feet. The condition is classified into several subtypes based on the anatomical location of the extra digit: preaxial polydactyly (extra digit on the thumb or great toe side), postaxial polydactyly (extra digit on the little finger or small toe side), and central polydactyly (duplication of the central digits). Postaxial polydactyly is the most common form and is particularly prevalent in individuals of African descent. The extra digits may range from fully formed, functional fingers or toes with normal bone structure to small, rudimentary soft tissue nubs (pedunculated postminimi). The condition is typically apparent at birth and is usually painless, though the extra digits may cause functional difficulties, cosmetic concerns, or problems with footwear. Several genes have been implicated in non-syndromic polydactyly, including GLI3, ZNF141, MIPOL1, PITX1, and mutations in the ZRS (zone of polarizing activity regulatory sequence) enhancer of the SHH gene, among others. The inheritance pattern varies by subtype but is most commonly autosomal dominant with variable expressivity and incomplete penetrance. Treatment is primarily surgical and is generally performed in early childhood. Rudimentary digits attached by a narrow stalk may be removed by simple ligation or minor surgical excision shortly after birth. More complex duplications involving bone, joints, tendons, and ligaments require reconstructive surgery to remove the extra digit while preserving optimal hand or foot function and appearance. Outcomes are generally excellent, and most individuals with non-syndromic polydactyly lead fully normal lives with no long-term functional impairment after appropriate surgical correction.

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