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长QT综合征的基因检测：区分致病性突变与良性变异
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Genetic Testing for Long-QT Syndrome: Distinguishing Pathogenic Mutations From Benign Variants
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Kapa S, Tester DJ, Salisbury BA
2010/1/28 17:10:06
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Circulation,
2009,
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View at Publisher
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Background:
Genetic testing for long-QT syndrome (LQTS) has diagnostic, prognostic, and therapeutic implications. Hundreds of causative mutations in 12 known LQTS-susceptibility genes have been identified. Genetic testing that includes the 3 most commonly mutated genes is available clinically. Distinguishing pathogenic mutations from innocuous rare variants is critical to the interpretation of test results. We sought to quantify the value of mutation type and gene/protein region in determining the probability of pathogenicity for mutations.
Methods and Results:
Type, frequency, and location of mutations across KCNQ1 (LQT1), KCNH2 (LQT2), and SCN5A (LQT3) were compared between 388 unrelated “definite” (clinical diagnostic score ≥4 and/or QTc ≥480ms) cases of LQTS and >1300 healthy controls for each gene. From these data, estimated predictive values (percent of mutations found in definite cases that would cause LQTS) were determined according to mutation type and location. Mutations were 10 times more common in cases than controls (0.58 per case versus 0.06 per control). Missense mutations were the most common, accounting for 78%, 67%, and 89% of mutations in KCNQ1, KCNH2, and SCN5A in cases and >95% in controls. Nonmissense mutations have an estimated predictive value >99% regardless of location. In contrast, location appears to be critical for characterizing missense mutations. Relative frequency of missense mutations between cases and controls ranged from ≈1:1 in the SCN5A interdomain linker to infinity in the pore, transmembrane, and linker in KCNH2. These correspond to estimated predictive values ranging from 0% in the interdomain linker of SCN5A to 100% in the transmembrane/linker/pore regions of KCNH2. The estimated predictive value is also high in the linker, pore, transmembrane, and C terminus of KCNQ1 and the transmembrane/linker of SCN5A.
Conclusions:
Distinguishing pathogenic mutations from rare variants is of critical importance in the interpretation of genetic testing in LQTS. Mutation type, mutation location, and ethnic-specific background rates are critical factors in predicting the pathogenicity of novel mutations. Novel mutations in low–estimated predictive value regions such as the interdomain linker of SCN5A should be viewed as variants of uncertain significance and prompt further investigation to clarify the likelihood of disease causation. However, mutations in regions such as the transmembrane, linker, and pore of KCNQ1 and KCNH2 may be defined confidently as high-probability LQTS-causing mutations. These findings will have implications for other genetic disorders involving mutational analysis.
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疾病资源中心
病例分析 [栏目介绍]
曹晶珠 邹大进
解放军第二军医大学附属长海医院内分泌科
患者为中年女性，35岁，因“多饮、多尿、全身乏力、闭经1年，体重增加、肝区不适半年”于2008年8月入院。患者2007年感冒后出现多饮、多尿，每日饮水约10,000 ml，未予重视及诊治。2007年出现闭经，在外院妇产科就诊，先后予2次黄体酮肌肉注射，仍未来月经。半年前体重增加25 kg，肝区不适，肝功能示转氨酶升高。患者无便秘腹胀、无皮肤感染、无双下肢水肿，活动后稍感胸闷、气喘，夜尿增多，平均每小时1次。最大体重88.7 kg。既往史无特殊。月经史：初潮14岁，4/28～30，2008年6月。
医学数据库
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