Because polydactyly is relatively common, Castilla et al analyzed its association with other congenital anomalies. From 1967–1993, 5,927 (1.89 per 1,000) polydactyly cases were identified among 3,129,297 consecutive registered births weighing more than 500g in Brazil and Argentina. The polydactyly was classified as duplicated fifth digit (postaxial), duplicated first digit (preaxial type-I) and rare types. In addition, the patients were grouped into isolated or associated, depending on the presence or absence of other congenital anomalies. The associated cases were further subdivided into combined, if the other defect was a limb defect; syndromic, if there was a recognizable pathogenic entity; and multiple congenital anomaly (MCA), if there was no recognized entity. Polydactyly was found to be associated with other congenital anomalies in 14.6% of the cases. Among these, the polydactyly was postaxial in 11.8%, preaxial-I in 20%, and rare in 54.9%. Duplication of the fifth toe plus syndactyly of the fourth and fifth toes and syndactyly adjacent to a duplicated digit were most common. Trisomy 13, Down Syndrome, and Meckel Syndrome represented 255 of the 338 syndromic polydactyly cases. Down Syndrome was strongly associated with preaxial polydactyly and negatively associated with postaxial polydactyly.
Polydactyly is a relatively common congenital anomaly (nearly 2 per 1,000 in this study), and determination of its significance, if any, is the responsibility of the pediatrician. Polydactyly has been listed as a frequent component of at least 16 syndromes and an occasional finding in 31 syndromes.1 This study organizes the types of polydactyly, delineates associations with other malformations, and highlights the importance of syndromic associations. Because 5.7% of the polydactyly cases were part of a syndrome, a search for associated abnormalities is warranted, especially with a rare polydactyly. If physical examination demonstrates dysmorphic features and/or if the patient has an unusual form of polydactyly, ultrasonography and other radiological procedures are indicated to detect possible heart, renal, brain, and skeletal anomalies in order to eliminate the possibility of a coexisting syndrome or significant associated anomalies. If other congenital malformations or dysmorphic features are found, chromosome analysis is indicated because of the frequency of Trisomy 13 and Down Syndrome in infants with polydactyly. The polydactyly of Meckel Syndrome is usually postaxial and associated with an occipital encephalocele and cystic dysplasia of the kidneys.2
This paper and the commentary point a “finger” (or two) at when we need to do a further workup on children with polydactyly and what constitutes that workup.