染色体病是直接引起儿童智力低下(MR)的主要原因之一。其中常染色体异常占染色体病的90%,而性染色体异常则占10%。性染色体异常包括数目异常及结构异常。一般认为,性染色体异常儿童无智力低下的表型,而是以青春期第二性征不发育为主要表现,所以在年幼儿中很少能早期发现,确定诊断。我室在咨询门诊的1469例儿童中发现22例儿童 Chromosomal disease is one of the main causes of mental retardation (MR) in children. Of them, autosomal abnormalities account for 90% of chromosomal diseases, while sex chromosome abnormalities account for 10%. Sexual chromosomal abnormalities include a number of abnormalities and structural abnormalities. It is generally believed that children with abnormal sex chromosome abnormalities without mental retardation phenotype, but with adolescent secondary sexual development is not as the main performance, so very few young children can be found early to confirm the diagnosis. Twenty-two children were found in 1,469 children in our consultation clinic