Triphalangeal thumb SNOMEDCT_US:205308004 The requirement for a single PD axis relates to the issue that partial forms of Preaxial polydactyly may comprise a partially duplicated thumb with two distal phalanges and a single proximal phalanx. That finding is instead coded as a mild form of thumb polydactyly. Note that this finding can be readily assessed by examination and/or physical manipulation of the thumb. HP:0006194 Triphalangeal thumbs Finger-like thumb UMLS:C0241397 Triphalangy of thumb HP:0005846 HP:0009619 Digitalized thumb Accessory phalanx of the 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. HP:0009610 Abnormality of thumb phalanx