Christensen K, Fogh-Andersen P
Genetic Epidemiologic Research Unit, Odense University, Denmark.
Am J Med Genet. 1993 Nov 1;47(6):910-6. doi: 10.1002/ajmg.1320470620.
A classical twin study is one of the best methods to address the open question of the role of genes and environment in the cause of cleft lip with or without cleft palate [CL(P)]. In addition, when twin concordance rates are combined with information about the risk for CL(P) to more remote relatives, they can help to establish the most likely mode of inheritance for CL(P). The present study was based on three nation wide ascertainment sources of CL(P) in twins in Denmark during the period 1970-1990. The Danish surgical files were found suitable for ascertaining twins with non-syndromic CL(P) and a total of 39 pairs was identified through these files. In more than 70% of the cases, the zygosity assignment was based on unlike-sex or an extensive panel of blood, serum, and enzyme types. More mono- and dizygotic twin (CL(P) cases than expected were found, although the difference was not significant. The proband concordance rate for CL(P) was 60% in monozygotic twins and 10% in dizygotic twins; six cases were of unknown zygosity. This finding indicates that genetic factors play a major role in the cause of CL(P) but environmental and/or stochastic factors are probably acting too. When the familial recurrence patterns analyzed by Mitchell and Risch [1992: Am J Hum Genet 51:323-332] are interpreted in light of these new estimates of monozygotic concordance, they provide further evidence for the finding that no single locus can account for more than a six-fold increase in risk to first-degree relatives.
经典双胞胎研究是解决基因和环境在唇裂伴或不伴腭裂（CL(P)）病因中作用这一开放性问题的最佳方法之一。此外，当双胞胎一致性率与关于CL(P)在更远亲属中的风险信息相结合时，它们有助于确定CL(P)最可能的遗传模式。本研究基于1970 - 1990年丹麦全国范围内的三个双胞胎CL(P)确诊来源。发现丹麦的外科手术档案适合用于确诊非综合征性CL(P)双胞胎，通过这些档案共识别出39对双胞胎。在超过70%的病例中，合子性判定基于不同性别或广泛的血型、血清型和酶型组合。发现单卵和双卵双胞胎（CL(P)病例）比预期的多，尽管差异不显著。单卵双胞胎中CL(P)的先证者一致性率为60%，双卵双胞胎中为10%；有6例合子性未知。这一发现表明遗传因素在CL(P)病因中起主要作用，但环境和/或随机因素可能也在起作用。当根据这些新的单卵一致性估计来解释Mitchell和Risch [1992: 《美国人类遗传学杂志》51:323 - 332] 分析的家族复发模式时，它们为“没有单个基因座能使一级亲属的风险增加超过六倍”这一发现提供了进一步证据。
