Pericentric inversion of chromosome 11 in one of two similar retarded brothers.

We report two brothers, aged 2k and 4i, with similar features, namely developmental delay, short stature, and small delicate facies. Chromosome analysis revealed a pericentric inversion of chromosome 11 in one boy and a normal karyotype in the other. The father was shown to be the carrier of this pericentric inversion. Two brothers with mental retardation, particularly in the area of speech development, were assessed for aetiological factors. Examination revealed that both were short, the younger boy being below the 3rd centile and the older one below the 10th centile for height, while the parents, grandparents, and two older normal sibs were on the 75th centile for height. In both, the facies were small and delicate with prominent bossed forehead. There were no other congenital abnormalities. In both cases pregnancy and delivery were normal, as were their birthweights. There was no apparent exposure to terato-