Opitz C trigonocephaly syndrome and midline brain anomalies.

We describe a child with trigonocephaly, strabismus, upslanting palpebral fissures, nasal bridge hypoplasia, hypertrophic alveolar ridges and large gingivo-labial frenula, short neck, hip "dysplasia," equinovarus deformities, cryptorchidism, atrial septal defect ostium secundum, and severe mental retardation, findings consistent with C syndrome. The patient also had a Dandy-Walker malformation, complete callosal agenesis, and occipital meningocele. These structural defects are independent of the premature closure of the metopic suture, and confirm that midline brain anomalies are part of C syndrome. The hypothesis that the basic developmental defect in this syndrome primarily affects the midline field is supported by the concomitance of other anomalies, such as conotruncal heart defects, omphalocele, and genital anomalies.