Holoprosencephaly-postaxial polydactyly syndrome associates, in chromosomally normal neonates, holoprosencephaly, severe facial dysmorphism, postaxial polydactyly and other congenital abnormalities, suggestive of trisomy 13 (see this term).

Supernumerary digits located at the ulnar side of the hand (that is, on the side with the fifth finger).