Holoprosencephaly and polydactyly: a possible expression of the hydrolethalus syndrome.

We report two fetuses with hydrocephalus, features of holoprosencephaly, and postaxial polydactyly born to a consanguineous Mexican-American couple. The phenotype is consistent with the hydrolethalus syndrome, although holoprosencephaly has not previously been seen in this condition. We believe other similar cases with a trisomy 13 phenotype but normal chromosomes may also have the hydrolethalus syndrome.