Holoprosencephaly in monozygotic twins - clinical and computer tomographic findings.

Of monozygotic male twins with holoprosencephaly, one showed by computer tomographic (CAT) scan a mild type with orbital hypotelorism, flat nose, bilateral cleft lip, and cleft palate associated with an intermaxillary rudiment. By CAT scan, the other boy had the alobar type with marked orbital hypotelorism, flat nose, absent nasal bridge, and median cleft lip. Lymphocyte chromosomes were apparently normal. A review of the literature shows a heterogeneous patient material in that most pertinent cases involved dizygotic twins, and some of these presumably had chromosome abnormalities.