Happle Rudolf
Department of Dermatology, Philipp University of Marburg, Marburg, Germany.
J Am Acad Dermatol. 2007 Oct;57(4):690-9. doi: 10.1016/j.jaad.2007.06.039.
In common acquired skin disorders with a polygenic background such as psoriasis, a linear or otherwise segmental arrangement may sometimes be noted. The segmental involvement tends to be rather severe and may be associated with milder, nonsegmental lesions of the same disorder. Such cases may be best explained by an early postzygotic event in the form of loss of heterozygosity involving one of the genes that predispose to the disorder. The following pertinent examples are reviewed in this article: psoriasis vulgaris, pustular psoriasis, atopic dermatitis, lichen planus, systemic lupus erythematosus, pemphigus vulgaris, vitiligo, graft-versus-host disease, granuloma annulare, erythema multiforme, and drug eruption to ibuprofen. Such cases should not be categorized as a "type 2 segmental manifestation" because this term exclusively applies to monogenic traits, whereas in polygenic disorders the more descriptive term "superimposed segmental manifestation" seems appropriate. The concept of early loss of heterozygosity offers a plausible explanation as to why: the segmental involvement tends to appear at a rather young age and often precedes the development of milder, nonsegmental lesions of the same disorder; the segmental lesions are notoriously difficult to treat; and family members may show the disorder in its nonsegmental form. On the other hand, the theory of isolated versus superimposed segmental manifestation may help to elucidate the origin of polygenic skin disorders at the molecular level.
在具有多基因背景的常见获得性皮肤病中，如银屑病，有时可观察到线性或其他节段性分布。节段性受累往往较为严重，可能与同一疾病较轻的非节段性损害相关。此类病例最好用合子后早期事件来解释，即涉及一种易患该疾病的基因的杂合性缺失。本文回顾了以下相关实例：寻常型银屑病、脓疱型银屑病、特应性皮炎、扁平苔藓、系统性红斑狼疮、寻常型天疱疮、白癜风、移植物抗宿主病、环状肉芽肿、多形红斑以及对布洛芬的药疹。此类病例不应归类为“2型节段性表现”，因为该术语专门用于单基因性状，而在多基因疾病中，更具描述性的术语“叠加节段性表现”似乎更为合适。杂合性早期缺失的概念为以下情况提供了一个合理的解释：节段性受累往往在相当年轻时出现，且常常先于同一疾病较轻的非节段性损害的发生；节段性损害 notoriously 难以治疗；家庭成员可能表现出该疾病的非节段性形式。另一方面，孤立性与叠加性节段性表现的理论可能有助于在分子水平阐明多基因皮肤病的起源。
