Department of Anesthesiology, Intensive Care Medicine and Pain Therapie, University of Wuerzburg, Oberduerrbacher Straße 6, 97080, Wuerzburg, Germany.
Department of Anesthesiology, Intensive Care Medicine and Pain Therapy, University of Frankfurt, Goethe University, Theodor-Stern-Kai 7, 60590, Frankfurt, Germany.
Sci Rep. 2021 Feb 9;11(1):3445. doi: 10.1038/s41598-021-82024-7.
Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle metabolism characterized by generalized muscle rigidity, increased body temperature, rhabdomyolysis, hyperkalemia and severe metabolic acidosis. The underlying mechanism of MH involves excessive Ca release from myotubes via the ryanodine receptor type 1 (RYR1) and the voltage-dependent L-type calcium channel (CACNA1S). As more than 300 variants of unknown significance have been detected to date, we examined whether freely available pathogenicity prediction tools are able to detect relevant MH causing variants. In this diagnostic accuracy study, blood samples from 235 individuals with a history of a clinical malignant hyperthermia or their close relatives were genetically screened for RYR1 variants of all 106 RYR1 exons and additionally for known variants of CACNA1S. In vitro contracture tests were conducted on muscle biopsies obtained from all individuals, independently of whether a pathogenic variant, a variant of unknown significance or no variant was detected. Comparisons were made to three established bioinformatic pathogenicity detection tools to identify the clinical impact of the variants of unknown significance. All detected genetic variants were tested for pathogenicity by three in silico approaches and compared to the in vitro contracture test. Sensitivity and specificity of exon screening of all individuals listed in our MH database was analyzed. Exon screening identified 97 (41%) of the 235 individuals as carriers of pathogenic variants. Variants of unknown significance were detected in 21 individuals. Variants of unknown significance were subdivided into 19 malignant-hyperthermia-susceptible individuals and 2 non-malignant-hyperthermia-susceptible individuals. All pathogenic variants as well as the malignant-hyperthermia-suspectible variants were correctly identified by the bioinformatic prediction tools. Sensitivity of in silico approaches ranged between 0.71 and 0.98 (Polyphen 0.94 [CI 95% 0.75; 0.99]; Sift 0.98 [CI 95% 0.81; 0.99]; MutationTaster 0.92 [CI 95% 0.75; 0.99]). Specificity differed depending on the used tool (Polphen 0.98 [CI 95% 0.32; 0.99]; Sift 0.98 [CI 95% 0.32; 0.99]; MutationTaster 0.00 [CI 95% 0.00; 0.60]). All pathogenic variants and variants of unknown significance were scored as probably damaging in individuals, demonstrating a high sensitivity. Specificity was very low in one of the three tested programs. However, due to potential genotype-phenotype discordance, bioinformatic prediction tools are currently of limited value in diagnosing pathogenicity of MH-susceptible variants.
恶性高热（MH）是一种骨骼肌代谢的遗传性疾病，其特征为全身肌肉僵硬、体温升高、横纹肌溶解、高钾血症和严重代谢性酸中毒。MH 的潜在机制涉及肌管通过兰尼碱受体 1（RYR1）和电压依赖性 L 型钙通道（CACNA1S）从肌球蛋白中过度释放 Ca。迄今为止，已经检测到 300 多种具有未知意义的变异，因此我们检查了免费的致病性预测工具是否能够检测到相关的 MH 致病变异。在这项诊断准确性研究中，对 235 名有临床恶性高热史或其近亲的个体的血液样本进行了 RYR1 所有 106 个外显子的变异筛选，并对 CACNA1S 的已知变异进行了筛选。对所有个体的肌肉活检进行了体外挛缩试验，无论是否检测到致病变异、具有未知意义的变异或无变异。与三种已建立的生物信息学致病性检测工具进行了比较，以确定具有未知意义的变异的临床影响。通过三种计算机模拟方法对所有检测到的遗传变异进行了致病性检测，并与体外挛缩试验进行了比较。分析了我们 MH 数据库中列出的所有个体的外显子筛选的敏感性和特异性。外显子筛选鉴定出 235 名个体中有 97 名（41%）为致病性变异携带者。在 21 名个体中检测到具有未知意义的变异。具有未知意义的变异分为 19 名恶性高热易感个体和 2 名非恶性高热易感个体。所有致病性变异以及恶性高热可疑变异均被生物信息学预测工具正确识别。计算机模拟方法的敏感性在 0.71 到 0.98 之间（Polyphen 0.94 [95%CI 0.75; 0.99]；Sift 0.98 [95%CI 0.81; 0.99]；MutationTaster 0.92 [95%CI 0.75; 0.99]）。特异性取决于所用的工具（Polyphen 0.98 [95%CI 0.32; 0.99]；Sift 0.98 [95%CI 0.32; 0.99]；MutationTaster 0.00 [95%CI 0.00; 0.60]）。在个体中，所有致病性变异和具有未知意义的变异均被评为可能具有破坏性，表明敏感性较高。在三个测试程序中的一个中，特异性非常低。然而，由于潜在的基因型-表型不一致，生物信息学预测工具目前在诊断 MH 易感变异的致病性方面价值有限。
