Krahn Timothy
Novel Tech Ethics, Bioethics Department, Dalhousie University, Intellectual Commons, 1234 LeMarchant St., Halifax, Nova Scotia, Canada.
Med Health Care Philos. 2009 Jun;12(2):187-202. doi: 10.1007/s11019-008-9171-x. Epub 2008 Nov 1.
The identification and avoidance of disease susceptibility in embryos is the most common goal of preimplantation genetic diagnosis (PGD). Most jurisdictions that accept but regulate the availability of PGD restrict it to what are characterized as 'serious' conditions. Line-drawing around seriousness is not determined solely by the identification of a genetic mutation. Other factors seen to be relevant include: impact on health or severity of symptoms; degree of penetrance (probability of genotype being expressed as a genetic disorder); potential for therapy; rate of progression; heritability; and age of onset. In the original applications of PGD, most, if not all of these factors were seen as necessary but none was seen as sufficient for determining whether a genetic condition was labelled 'serious'. This, however, is changing as impact on health or severity of symptoms is coming to eclipse the other considerations. This paper investigates how age of onset (primarily in the context of the United Kingdom (UK)) has become considerably less significant as a criterion for determining ethically acceptable applications of PGD. Having moved off the threshold of permitting PGD testing for only fatal (or seriously debilitating), early-onset diseases, I will investigate reasons for why age of onset will not do any work to discriminate between which adult-onset diseases should be considered serious or not. First I will explain the rationale underpinning age of onset as a factor to be weighed in making determinations of seriousness. Next I will challenge the view that later-onset conditions are less serious for being later than earlier-onset conditions. The final section of the paper will discuss some of the broader disability concerns at stake in limiting access to PGD based upon determinations of the 'seriousness' of genetic conditions. Instead of advocating a return to limiting PGD to only early-onset conditions, I conclude that the whole enterprise of trying to draw lines of what is to count as a 'serious' condition is itself problematic and in certain ways morally misleading.
识别并避免胚胎中的疾病易感性是植入前基因诊断（PGD）最常见的目标。大多数接受并规范PGD应用的司法管辖区将其限制在所谓的“严重”疾病范围内。对严重性的界定并非仅由基因突变的识别来决定。其他被认为相关的因素包括：对健康的影响或症状的严重程度；外显率（基因型表现为遗传疾病的概率）；治疗潜力；病情进展速度；遗传度；以及发病年龄。在PGD的最初应用中，这些因素中的大多数（如果不是全部的话）都被视为必要因素，但没有一个因素被认为足以确定一种遗传疾病是否被标记为“严重”。然而，随着对健康的影响或症状的严重程度开始超越其他因素的考量，这种情况正在发生变化。本文探讨了发病年龄（主要是在英国的背景下）作为确定PGD在伦理上可接受应用的标准，其重要性已大幅降低的情况。在不再仅允许对致命（或严重致残）的早发性疾病进行PGD检测之后，我将研究为什么发病年龄无法用于区分哪些成人发病疾病应被视为严重疾病的原因。首先，我将解释将发病年龄作为在确定严重性时需权衡的一个因素的基本原理。接下来，我将质疑那种认为晚发性疾病因其发病晚于早发性疾病就不那么严重的观点。本文的最后一部分将讨论基于对遗传疾病“严重性”的判定来限制PGD获取所涉及的一些更广泛的残疾问题。我并非主张回归到仅将PGD限制用于早发性疾病的做法，而是得出结论认为，试图划定什么算作“严重”疾病的整个做法本身就存在问题，并且在某些方面具有道德误导性。
