Mutations in Sonic hedgehog (SHH) cause holoprosencephaly
Holoprosencephaly is a rare malformation sequence in which the basic feature is impaired midline cleavage of the embryonic forebrain (Gorlin et al, 1990). It is an etiologically heterogenous condition; teratogenic and genetic factors may both be responsible. The phenotype varies widely; the facial dysmorphism includes cyclopia, hypertelorism, single nostril or flat nose, cleft lip, and hypodontia. A single maxillary central incisor can be seen as the mildest phenotype of holoprosencephaly. In familial cases, an autosomal dominant inheritance with reduced penetrance has been observed (Odent et al, 1998). At least 12 different loci have been associated with holoprosencephaly and several distinct genes identified (Wallis et al, 2000).
Text adapted from Sirpa Arte: Phenotypic and genotypic features of familial hypodontia. Dissertation, Institute of Dentistry, University of Helsinki, Finland, 2001.
Text last edited 09.10.2003 by P.N. , page last created 10.12.2004 by P.N.