前两天看《阿甘正传》，电影挺好。小时候的阿甘长一对明显的招风耳，长长的脸，越看越有点像脆性X综合征患儿的表型。但是鉴于我们的阿甘最后越长越正常，到电影最后居然还讲了一大通富有哲理的话，而且还生了个聪明伶俐的儿子，我想我还是暂时不把什么综合征之类的往人家身上乱套了。今天介绍一下智力障碍的发病率，其实它的发病率还是挺高的。全世界在智障病人身上花的钱比其它疾病：高血压、心脏病、糖尿病等要高得多。智障中最常见的是X-连锁的类型，今天就介绍这个吧。

X-LINKED MENTAL RETARDATION

H.-Hilger Ropers* and Ben C. J. Hamel‡

X-连锁的智力障碍

Abstract | Genetic factors have an important role in the aetiology of mental retardation. However, their contribution is often underestimated because in developed countries, severely affected patients are mainly sporadic cases and familial cases are rare. X-chromosomal mental retardation is the exception to this rule, and this is one of the reasons why research into the genetic and molecular causes of mental retardation has focused almost entirely on the X-chromosome. Here, we review the remarkable recent progress in this field, its promise for understanding neural function, learning and memory, and the implications of this research for health care.

摘要：遗传因素是导致智力障碍的一个重要因素。然而，这个因素却常常被低估。因为在发达国家，严重的智障患者多为散发病例，家族性的病例较为罕见。但是X-染色体导致的智力障碍却是例外。这正是为什么智障的遗传及分子病因研究几乎全部集中在X染色体上的原因之一。在此，我们对该领域近期所取得的重大进展进行回顾，并总结这些进展对于了解神经生物学功能、行为、记忆，以及对医疗卫生事业的意义。

Mental retardation is one of the main reasons for referral in paediatric, child-neurological and clinical genetic practice. Often, however, despite extensive investigations, an aetiological diagnosis cannot be made, leaving families without accurate genetic counselling or reproductive options, such as prenatal diagnosis. The prevalence of mental retardation in developed countries is thought to be on the order of 2–3% (REF. 1), although estimates vary widely, particularly for mild mental retardation. In central Europe, about 8% of healthcare expenditure is spent on ‘mental handicaps’ as defined by the International Classification of Disease (ICD) (BOX 1), which by far exceeds the costs that are related to all other ICD categories2. Together with its high burden for society and families, this renders mental retardation one of the most important unsolved problems in medicine.

智力障碍是儿科、儿童神经科和临床遗传科最常见的病症之一。虽然针对智障的诊断方法多种多样，但是依然有很多病人还是无法找出病因，因此患者及其家属不能得到准确的遗传咨询和再生育咨询，因此产前诊断也就不可能了。虽然人们对智障的发病率说法不一，尤其在中度智力障碍的发病率上尤有分歧，但是普遍的观点是发达国家的智障发病率约为2%-3%。若根据国际疾病分类体系来界定智障病人，那么在中欧，用于智力障碍病人的医疗费用大约占了总医疗支出的8%。此外智障还给社会和家庭造成了极大的负担。因此，智力障碍已成为医学界亟待解决的一大难题。