Il cariotipo in pazienti con diagnosi clinica di sindrome di Down: Valutazione di un campione di 1588 soggetti.

A collaborative study between genetic centers in North East Italy was performed. Data on all subjects who underwent a citogenetic examination because of clinical suspect of Down syndrome from 1973 to 1985 were analyzed. All data regarding sex, age at clinical observation and karyotype are presented in table 1 . The incidente of trisomy 21 and other chromosomal abnormalities is 4, 5%. A mosaic was detected in 1.34 % of karyotype. All data are in agreement with the literature. The foilowing considerations can be obtained by data regarding karyotype/phenotype correlation, sex and age at clinical observation of the subjects: 1) the male/female ratio (1 . 24/1) significantly differs from that of normal population (p < 0 .025). The ratio does not change with the increasing of the subjects age. There is no a selection sex durìng postnatal life ; 2) a higher proportion of female rather than male (p < 0 .001) with clinical diagnosis of Down syndrome have a normal karyotype. The Authors are not able to explain this latter observation.