Predictors of Syndromic Association in Ulnar Polydactyly: Analysis of a Multicenter Congenital Hand Differences Registry in the United States

Purpose Ulnar polydactyly is one of the most common congenital hand differences in the United States. Prior literature suggests that those with type B (rudimentary) extra digits, patients and caregivers that identify as Black race or skin color, and those with a strong family history of polydactyly are less frequently associated with concomitant genetic syndromes. As race is a social construct, not a biological one, there is a need to quantify the degree of association of other clinical variables with syndromes for risk stratification and testing. Methods Data from the Congenital Upper Limb Difference (CoULD) Registry were collected and reviewed, involving 10 tertiary hand centers in the United States. Demographic characteristics, morphology, and laterality were analyzed for to their relationship with syndromic and nonsyndromic forms of ulnar polydactyly. Results Three hundred thirty-four patients (42% female and 63% bilateral) were included in the cohort. Patients with type A (fully formed) polydactyly had an associated syndrome in 21% of cases, compared to 2% of type B ulnar polydactyly. Black patients were less likely to have an associated syndrome than non-Black patients, but with a less strong association than type B morphology. Patients without any family history of upper limb difference were more likely to have an associated syndrome. Bilateral cases were not associated with a syndrome. Conclusions A high frequency of genetic syndromes was found in patients with type A polydactyly (21%), and these patients were much more likely to have a genetic syndrome than those with rudimentary (type B) digits. Given this strong association with multiorgan genetic syndromes the authors recommend consultation with a genetics specialist for patients with type A ulnar polydactyly for early screening, diagnosis, treatment, and counseling for families. Type of study/level of evidence Prognostic II.