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.