The prevalence of chromosome diseases in the general population of Sichuan, China.

Chromosome abnormalities with recognizable clinical manifestations including mental retardation, primary infertility or primary amenorrhea of unknown etiology, abnormal sex differentiation and abnormal sex development were surveyed in the general population of Sichuan. The results showed that the prevalence of chromosome diseases in Sichuan was 31.5 per 100,000 of the general population with almost equal frequencies for autosomal chromosome and sex chromosome diseases. The most frequent autosomal chromosome disease was Down syndrome. The prevalence was 14.2 per 100,000 for the total population, and there should therefore be 154,000 cases of Down syndrome in the whole of China with its population of 1,100 million people. The most frequent sex chromosome diseases were Turner syndrome and Klinefelter syndrome. The prevalences were 14.3 and 14.1 per 100,000 for females and males, respectively. The majority of autosomal chromosome diseases clustered in the younger age groups, while the highest detection rate of sex chromosome diseases was found in the age group of 25-35, and thereafter it decreased with age. The age distribution of the cases indicates that both autosomal and sex chromosome diseases reduce the lifespan of patients.