Congenital finger anomalies are common with an incidence of 1 per 500 to 1,000 live births. The most common anomaly is polydactyly (duplication) followed by syndactyly (failure of differentiation). Presence of a congenital hand anomaly should alert the provider to perform a careful history and physical examination to evaluate for other associated malformations or syndromes. Congenital hand malformations are classified by embryologic origin and clinical manifestations. The major categories and representative examples include (1) failure of formation of parts (e.g., phocomelia, radial club hand), (2) failure of differentiation or separation of parts (e.g., syndactyly, clinodactyly, camptodactyly), (3) duplication (e.g., polydactyly), (4) overgrowth (e.g., macrodactyly), (5) undergrowth (e.g., thumb hypoplasia), and (6) congenital constriction band syndrome. A referral to a Pediatric Hand Specialist for further evaluation and surgical treatment is recommended for most congenital hand and digit anomalies.

• Approximately 80% of cases of syndactyly are sporadic. Males are affected twice as frequently as females. Complex syndactyly can be found as part of a syndrome, such as Poland or Apert syndrome.

• Clinodactyly is defined as abnormal curvature of the digit in the radioulnar plane. It rarely causes functional limitations. It may be seen as part of a syndromic condition, for example, Down syndrome (Trisomy 21).

• Camptodactyly refers to a congenital finger flexion deformity at the proximal interphalangeal (PIP) joint. There are two variants, one that appears in infancy with equal gender predilection and the other that presents in adolescent girls. Functional impairment is rare. The small finger is most commonly affected.

• Polydactyly is defined as preaxial (radial), central, or postaxial (ulnar). It may occur as an isolated malformation or as part of a syndrome, such as Trisomy 13 syndrome.

• Radial polydactyly (thumb duplication) occurs in 1 in every 12,000 live births with equal incidence in blacks and whites. The most common form of thumb duplication is complete duplication of the proximal and distal phalanges.

• Ulnar polydactyly is more common in blacks and is usually inherited in an autosomal dominant fashion without associated anomalies. In Caucasian patients, ulnar polydactyly may indicate serious chromosomal anomaly or associated malformations and should prompt further investigations.

• Ulnar polydactyly is subdivided into Type A (complete duplication up to the level of metacarpal head) and Type B (small rudimentary digit).

• Macrodactyly, or digital gigantism, reflects enlargement of all tissue elements of an involved digit. The index finger is most commonly affected. Two forms have been described: (1) static, with digit enlargement at birth with subsequent growth proportionate to the child; and (2) progressive, with disproportionate enlargement with age.

• Hypoplastic thumb malformation may be isolated or as part of a broader radial deficiency. When radial deficiency is present, detailed evaluation to exclude associated abnormalities, such as VACTERL (Vertebral anomalies, Anal atresia, Cardiac defects, Tracheoesophageal fistula and/or Esophageal atresia, Renal and radial anomalies, and Limb defects) syndrome, thrombocytopenia with absent radius (TAR) syndrome, Fanconi anemia, or Holt–Oram syndrome, is critical.

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