Hou J W, Wang T R, Chuang S M
Department of Pediatrics, National Taiwan University Hospital, Taipei.
J Intellect Disabil Res. 1998 Apr;42 ( Pt 2):137-43. doi: 10.1046/j.1365-2788.1998.00104.x.
A large-scale cytogenetic study of the causes of intellectual disability (ID) in children from special schools and institutions was made in Taiwan between 1991 and 1996. The screening methods and the identification of subjects with ID consisted of both clinical evaluation (i.e. photographs, questionnaires on family, pre-, peri- and postnatal history, and hospital records, including IQ) and further laboratory studies for diagnosis (i.e. standard chromosome analysis, and if indicated, high-resolution banding, cytogenetic fragile-X study or molecular techniques). A total of 11,892 patients were enrolled in this study. After excluding the acquired causes of ID, such as infections and the sequelae of brain insults, or the well-known single-gene disorders and other multifactorial diseases, 4372 (36.8%) cumulative cases were recruited for karyotyping studies according to their phenotypes and medical records. Abnormal karyotypes were noted in 1889 children (43.2% of all selected children). Thus, the overall incidence of chromosomal aberrations in subjects with ID was estimated as 15.9%. Down's syndrome, the most common cause of ID, accounted for 82.4% of all patients with abnormal karyotypes. The causes of ID were considered to be prenatal in 55.2% (n = 6564) of cases, perinatal in 9.5% (n = 1130), postnatal in 3.3% (n = 392) and unknown in 32.0% (n = 3805) of cases. Two large groups were classified: (1) serious ID (37%), including profound, severe and moderate categories; and (2) mild ID (63%). The causes (pre-, peri- and postnatal, and unknown) in these two populations were: 70%, 10.5%, 5.4% and 14.1%, and 46.5%, 8.9%, 2.1% and 42.5%, respectively. Genetic causes accounted for 38.5% (n = 4578) of all cases in this study, including 1557 with Down's syndrome, 233 with fragile-X syndrome, 199 with other various chromosomal abnormalities (i.e. unbalanced translocation, supernumerary markers and structural rearrangements), 238 with a defined or presumed single-gene defect, and 98 with a recognized contiguous gene syndrome (Prader-Willi, 56; Angelman, 34; Williams, 5; and Kallmann, 3); 2120 cases had familial ID. Multiple anomalies of undefined pattern, but without chromosomal aberration, infantile autism, ID of normal phenotype or family history, were of the other categories. Patients with a single-gene disorder or chromosomal aberration, especially those with unbalanced translocated or rearranged chromosomes, had genetic counselling and family studies. Pre-screening with photographs and questionnaires may give a better costbenefit than blind mass cytogenetic studies for each individual with ID.
1991年至1996年期间，台湾对来自特殊学校和机构的儿童智力残疾（ID）病因进行了大规模细胞遗传学研究。ID受试者的筛查方法和鉴定包括临床评估（即照片、家庭问卷、产前、围产期和产后病史以及医院记录，包括智商）以及进一步的实验室诊断研究（即标准染色体分析，如有必要，进行高分辨率显带、细胞遗传学脆性X研究或分子技术）。本研究共纳入11892例患者。排除ID的后天性病因，如感染和脑损伤后遗症，或已知的单基因疾病和其他多因素疾病后，根据其表型和病历，招募了4372例（36.8%）累积病例进行核型分析研究。1889名儿童（占所有选定儿童的43.2%）发现核型异常。因此，ID受试者染色体畸变的总体发生率估计为15.9%。唐氏综合征是ID最常见的病因，占所有核型异常患者的82.4%。ID的病因在55.2%（n = 6564）的病例中被认为是产前的，9.5%（n = 1130）是围产期的，3.3%（n = 392）是产后的，32.0%（n = 3805）是不明的。分为两大组：（1）重度ID（37%），包括深度、重度和中度类别；（2）轻度ID（63%）。这两组人群的病因（产前、围产期和产后以及不明）分别为：70%、10.5%、5.4%和14.1%，以及46.5%、8.9%、2.1%和42.5%。遗传病因占本研究所有病例的38.5%（n = 4578），包括1557例唐氏综合征、233例脆性X综合征、199例其他各种染色体异常（即不平衡易位、额外标记和结构重排）、238例明确或推测的单基因缺陷以及98例公认的连续性基因综合征（普拉德-威利综合征，56例；安吉尔曼综合征，34例；威廉姆斯综合征，5例；卡尔曼综合征，3例）；2120例有家族性ID。未明确模式但无染色体畸变、婴儿自闭症、正常表型或家族史的ID属于其他类别。患有单基因疾病或染色体畸变的患者，尤其是那些染色体不平衡易位或重排的患者，接受了遗传咨询和家系研究。与对每个ID个体进行盲目大规模细胞遗传学研究相比，通过照片和问卷进行预筛查可能具有更好的成本效益。
