Abstract
Two sisters are described. They are offspring of Arabic parents who are both first and second cousins, through both sets of grandparents; additionally the father's parents are first cousins. The diagnosis of agenesis of the corpus callosum in the propositae was made by the characteristic picture on the pneumoencephalogram. The clinical symptoms in the two sisters varied considerably. The older sister had shown delayed psychomotor development in infancy, mild mental retardation, and developed seizures at 7 years of age of both the grand mal and akinetic types. Her physical and neurological examination did not show any abnormalities. The EEG was severely abnormal with slow wave activity over the posterior parts of the brain and focal spiking. The younger sister presented at 6 months of age with failure to thrive, generalized hypotonia, but without seizures. Her EEG was within normal limits. This anomaly was probably transmitted by an autosomal recessive gene. The clinical and genetic aspects of this syndrome are discussed.