Studies of malformation syndromes of humans XXXIIIC: the FG syndrome - further studies on three affected individuals from the FG family.

The brain findings at autopsy of an 18-year-old male with FG syndrome were megalencephaly, midline fusion of mammillary bodies, heterotopia of neuroglial tissue in the 7th and 8th nerves, and ependymal cell replacement by neuroglial tissue as well as a diffuse defect of neuronal cell migration evidenced from pachygyria of many gyri, dysgenesis of cerebral cortex, and heterotopia of neurons in the white matter of the centrum ovale. A cousin, studied at 20 weeks' gestational age, had gross turridolichocephaly with enlarged cranium and also multiple minor external and internal anomalies. An affected brother of this fetus died at 17 months of complications of a congenital heart defect and CNS dysfunction. X-linked inheritance of the FG syndrome is confirmed.