One in 5000 live births. Many problems, microphthalmia, cleft lip and palate, polydactyly, developmental retardation, heart defects, etc. Cyclopia - extremely rare recessive inherited condition. Fusion of the eyes and the development of a tubular nose. Infants do not survive long after birth.
Mental development is absent.
Cranial development is suppressed. Microcephalic - Very uncommon. Grossly mentally retarded. Brain is severely underdeveloped. Cause uncertain, but may be a trisomy of the autosomes.