A form of preaxial polydactyly of fingers, a limb malformation syndrome, that is characterized by the presence of a usually opposable triphalangeal thumb with or without additional duplication of one or more skeletal components of the thumb. The thumb appearance can differ widely in shape (wedge to rectangular) or it can be deviated in the radio-ulnar plane (clinodactyly). PPD2 is also associated with systemic syndromes, including Holt-Oram syndrome and Fanconi anemia. The disease is polydactyly of a triphalangeal thumb (MONDO_0008270). Also known as: PPD2, polydactyly, preaxial type 2, polydactyly, preaxial type II, preaxial polydactyly type 2, triphalangeal thumb, type i.