- Triphalangeal thumb (HP:0001199): A thumb with three phalanges in a single, proximo-distal axis. Thus, this term applies if the thumb has an accessory phalanx, leading to a digit like appearance of the thumb. Evidence: PCS. Frequency: 11/12. (PMID:18178630)
- 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: PCS. Frequency: 3/12. (PMID:18178630)
- Congenital onset (HP:0003577): A phenotypic abnormality that is present at birth. Evidence: PCS. Frequency: 12/12. (PMID:18178630)
- Postaxial hand polydactyly (HP:0001162): Supernumerary digits located at the ulnar side of the hand (that is, on the side with the fifth finger). Evidence: PCS. Frequency: 4/12. (PMID:18178630)
- Finger syndactyly (HP:0006101): Webbing or fusion of the fingers, involving soft parts only or including bone structure. Bony fusions are referred to as "bony" Syndactyly if the fusion occurs in a radio-ulnar axis. Fusions of bones of the fingers in a proximo-distal axis are referred to as "Symphalangism". Evidence: PCS. Frequency: 5/12. (PMID:18178630)
- Autosomal dominant inheritance (HP:0000006): 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 heterozygotes. In the context of medical genetics, an autosomal dominant disorder is caused when a single copy of the mutant allele is present. Males and females are affected equally, and can both transmit the disorder with a risk of 50% for each child of inheriting the mutant allele. Evidence: PCS. (PMID:18178630)
- Broad thumb (HP:0011304): Increased thumb width without increased dorso-ventral dimension. Evidence: PCS. Frequency: 2/12. (PMID:18178630)
These phenotypes are associated with the disease triphalangeal thumb-polysyndactyly syndrome (OMIM:190605).