Single maxillary central incisor, holoprosencephaly, and holoprosencephaly-like phenotype.

Three patients--one with alobar holoprosencephaly and two with a holoprosencephaly-like phenotype--are reported with no identifiable mutations. In each case, one parent had a single maxillary central incisor (SMCI). We briefly review the holoprosencephaly-like phenotype and present a table of 25 conditions with SMCI.