- Preaxial hand polydactyly (HP:0001177): Supernumerary digits located at the radial side of the hand. Polydactyly (supernumerary digits) involving the thumb occurs in many distinct forms of high variability and severity. Ranging from fleshy nubbins over varying degrees of partial duplication/splitting to completely duplicated or even triplicated thumbs or preaxial (on the radial side of the hand) supernumerary digits. Evidence: TAS. (OMIM:174400)
- Radial deviation of thumb terminal phalanx (HP:0005895). Evidence: TAS. (OMIM:174400)
- Autosomal recessive inheritance (HP:0000007): A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele). Evidence: TAS. (OMIM:174400)
- Partial duplication of thumb phalanx (HP:0009944): A partial duplication, depending on severity leading to a broad or bifid appearance, affecting one or more of the phalanges of the thumb. As opposed to a complete duplication there is still a variable degree of fusion between the duplicated bones. Evidence: TAS. (OMIM:174400)
These phenotypes are associated with the disease polydactyly of a biphalangeal thumb (OMIM:174400).