Clinical manifestations and genetic aspects of true microcephaly.

Thirty-five cases of true microcephaly were found in a group of 3192 children with severe mental retardation in special institutions. In comparison to the general population the individuals with this congenital anomaly have not only much smaller dimensions of the cerebral cranium but also of the splanchnic cranium, although in a less significant degree. Body height and weight were found to be smaller as well. The neurological findings included, most frequently, slight abnormalities, in some cases hemiparesis was present. In the radiological findings an evident disproportion was observed between the cerebral and the facial parts of the cranium. A constant finding was mental retardation which was either profound or severe. True microcephaly is inherited as a recessive autosomal trait. The incidence of this condition in the Polish population is 28526 X 10(-6). The incidence of mutation of this gene is 14262 X 10(-6).