Holoprosencephaly: report of four cases and genotype-phenotype correlations.

Holoprosencephaly (HPE) is a heterogeneous disorder with variable expressivity and reduced penetrance. The causes vary from environmental factors to pure genetic forms, namely chromosomal and genomic abnormalities in up to 70% of the cases, and heterozygous mutations in at least four major genes in 17% of cases. We describe rare clinical findings, like craniovertebral hinge dysplasia, Hirschsprung’s disease and syringomyelia as part of the Currarino syndrome spectrum