Polydactyly

This neonate was born with an extra hypoplastic digit attached to the lateral aspect of the left little finger's middle phalanx. When informed of this anomaly on her daughter's hand, the mother registered neither shock nor surprise. Mother, grandmother, and other family members were similarly affected.

Duplicate middle and little fingers are often inherited as autosomal dominant defects. Fifth finger (postaxial) polydactyly is 10 times more common in blacks (1 in 300 persons) than in whites (1 in 3,000).

In contrast, white youngsters with little finger polydactyly have associated anomalies more frequently than black children. These disorders include syndactyly, triphalangeal thumb, polydactyly toes, cleft lip, hair lip, polycystic kidneys, imperforate anus, defective tibia, dwarfism, bladder obstruction, hemivertebrae, mental deficiency, heart defects, cataracts, hydrocephalus, deafness, eye defects, chronic nephritis, fingernail dystrophy, and hypogonadism.

Most of the duplicate digits are connected by a thread (ie, skin tag, type B postaxial polydactyly) and can be treated easily. As was done for this neonate, fine silk suture is used to ligate the extra digit at its base; the growth drops off within a few days. Excision and/or fulguration are other treatment options. Surgical excision, usually before 1 year of age, is needed to remove a well-formed extra digit.