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). The disease is Holoprosencephaly - postaxial polydactyly (Orphanet_2166). Also known as: Pseudo-trisomy 13 syndrome.