Opitz-C syndrome: on the nosology of mental retardation and trigonocephaly.

We report on two patients with a complicated form of trigonocephaly. The first patient has the Opitz-"C"-trigonocephaly syndrome. The second patient had initially a delayed motor development, but finally attained normal intelligence. A review of 22 patients with Opitz-C syndrome from the literature is presented. Most of the typical facial dysmorphism can be regarded as part of a trigonocephaly "sequence" rather than presenting characteristic features of a syndrome. More specific are the intra-oral anomalies, abnormally modelled ears, cardiac anomalies and neonatal hypotonia. All surviving patients are severely retarded. Since almost all patients are sporadic cases we suggest that the "C"-syndrome is a cytogenetically yet undetectable microdeletion syndrome.