Department of Ophthalmology, Ghent University Hospital, Ghent, Belgium.
Retina. 2011 Jun;31(6):1164-9. doi: 10.1097/IAE.0b013e3181fbcf2b.
Retinitis pigmentosa (RP) is a group of genetically heterogeneous diseases with progressive degeneration of the retina. The condition can be inherited as an autosomal dominant, autosomal recessive, and X-linked trait.
We report on two female twin pairs. One twin of each pair is affected with RP, the other twin is unaffected, both clinically and functionally.Molecular analysis in both twins included zygosity determination, arrayed primer extension chip analysis for autosomal recessive and dominant RP, sequencing of the entire RPGR gene, and analysis of X-chromosome inactivation status.
Both unrelated twin pairs were genetically identical. Of the potential pathogenetic mechanisms, skewed X-inactivation was excluded on leukocytes. Autosomal recessive RP and autosomal dominant RP arrayed primer extension chip analysis result was completely normal, excluding known mutations in known genes as the cause of disease in the affected twins. Sequencing excluded mutations in RPGR. A postzygotic recessive or dominant genetic mutation of an RP gene is not impossible. A postfertilization error as a potential cause of uniparental isodisomy is unlikely albeit not entirely impossible.
The authors report on the second and third unrelated identical twin pair discordant for RP. The exact cause of the condition and the explanation of the clinical discordance remain elusive.
色素性视网膜炎（RP）是一组具有视网膜进行性变性的遗传异质性疾病。该病可遗传为常染色体显性、常染色体隐性和 X 连锁特征。
我们报告了两例女性双胞胎。每对双胞胎中的一个受影响，另一个不受影响，在临床上和功能上均不受影响。对两个双胞胎进行了分子分析，包括确定同卵性、常染色体隐性和显性 RP 的阵列引物延伸芯片分析、整个 RPGR 基因测序以及 X 染色体失活状态分析。
两个无亲缘关系的双胞胎是完全相同的。在外周血白细胞中排除了偏性 X 染色体失活。常染色体隐性 RP 和常染色体显性 RP 阵列引物延伸芯片分析结果完全正常，排除了已知基因中的已知突变是受影响双胞胎疾病的原因。测序排除了 RPGR 突变。RP 基因的合子后隐性或显性遗传突变并非不可能。虽然并非完全不可能，但作为单亲二倍体潜在原因的受精后错误不太可能。
作者报告了第二和第三个不相关的同卵双胞胎对 RP 不一致的情况。该疾病的确切原因和临床不一致的解释仍不清楚。
