Etiological study of mental retardation in Budapest, Hungary.

The first complex etiological study of mental retardation in Budapest was carried out with 1,364 children ages 7 to 14 years. Of this sample, 1,060 attended special schools for mentally retarded children (47.5 percent), and 304 children lived in one of two residential training centers for moderately and severely retarded persons. Apart from the cases of unknown etiology (12.6 percent) and those who turned out to be "normal" (6.5 percent), approximately 50 percent of the index patients were classified as pathologically retarded, and the other 50 percent as familial--culturally retarded. Strictly genetic disorders (inborn errors of metabolism, malformation syndromes caused by single mutant genes, and autosome and sex chromosome abnormalities) accounted for 3.1, 4.0, 4.0, and 1.3 percent, respectively, of all cases. Pre-, peri-, and postnatal exogenic damage occurred in 1.8, 20.4, and 6.8 percent of the cases, respectively. Results were compared with findings from previous surveys in the United States and the United Kingdom.