Polydactyly: How many disorders and how many genes?

Disorders that include polydactyly as a manifestation are diverse and numerous. Cataloging these disorders by phenotype and genotype demonstrates numerous overlapping phenotypes, genetic heterogeneity of phenotypes, and distinct phenotypes generated from mutations in single genes. To assess these issues, a list of disorders with polydactyly has been compiled from several sources. Among 119 disorders, 39 disorders are associated with mutations in genes, and among these, genotypic and phenotypic overlap is demonstrated. These issues highlight the need for a diagnostic system that catalogs both genotype and phenotype.