USH2A基因变异耳聋患者临床特征分析

Genotypic and phenotypic characteristics of patients with USH2A variants

  • 摘要: 目的 本研究对临床常见的USH2A基因变异耳聋患者的基因型及表型进行分析,为实施精准的遗传咨询和干预指导提供参考。方法 对2015 - 2018年于解放军总医院耳鼻咽喉头颈外科就诊的547例感音神经性耳聋患者进行基因检测,筛选出USH2A基因变异耳聋患者,对USH2A基因变异位点致病性及常见的USH2A基因变异图谱及特点进行分析。并对患者进行耳科学及听力学检查,分析听力损失程度和听力图类型,以及年龄与听力损失程度的相关性。结果 共收集到10例USH2A基因变异耳聋患者,USH2A基因变异耳聋患者发现听力下降的中位年龄为6岁(7个月~ 13岁)。听力损失程度结果统计,轻度听力损失1例,中度听力损失1例,中重度听力损失6例,重度听力损失1例,极重度听力损失1例。部分患者听力损失程度随年龄进一步增加。听力损失表型结果:渐降型2例,平坦型3例,低频(125 ~ 500 Hz或125 ~ 1 000 Hz)陡降,中高频(500 ~ 8 000 Hz)平坦型5例。10例USH2A基因变异耳聋患者中共有22处变异,20个不同的USH2A基因变异位点,其中有10个位点为未曾被报道过的变异。其变异种类包括:3个剪切位点变异,c.5572+1G>A、c.14969-2A>G、c.15297+1G>A;3个移码突变,c.5548delT、c.62926296ATAAG>TA、c.7863delA;4个错义突变,c.T3364G、c.11279G>C、c.13876C>G、c.14225C>T。另外10个为报道过的变异,已知明确致病位点6个,分别为c.99100insT、c.187C>T、c.2797C>T、c.8559-2A>G、c.11156G>A、c.1510415105del。10例患者中2例携带USH2A c.99100insT位点,余变异位点均为1例。22处USH2A变异位点中,有3个位点位于2号外显子。结论 本研究发现了中国耳聋患者较为常见的USH2A基因变异位点c.99100insT,较常见的USH2A基因变异耳聋患者听力损失程度为中重度,较常见的听力损失类型为低频陡降、中高频平坦型,为USH2A基因变异耳聋患者早期诊断及早期干预、精准的遗传咨询提供了临床证据。

     

    Abstract: Objective To analyze the genotype and phenotype of patients with hearing loss and USH2A gene variants, in order to deliver precise genetic counseling. Methods USH2A variations were screened out from 547 patients with sensorineural hearing loss collected by genetic testing from 2015 to 2018 in Institute of Otolaryngology, Chinese PLA General Hospital. The pedigrees of patients with USH2A gene variant were drawn and their characteristics were analyzed. The pathogenicity of mutations were identified. Standard otology examination and audiological examination were carried out to analyze the degree of hearing loss and the type of hearing curve in patients with USH2A variants. The relationship between the age of onset and the degree of hearing loss was analyzed in patients with different USH2A gene mutations. Results We screened out 10 patients with USH2A gene variants from 547 patients with sensorineural hearing loss who underwent genetic testing, with a positive rate of 1.8%. The median age of hearing loss onset was 6 year-old (range, 7 months to 13 years). One case had mild hearing loss, 1 case had moderate hearing loss, 6 cases had moderate to severe hearing loss, 1 case had severe hearing loss, and 1 case had profound hearing loss. The hearing loss in some patients had further progressed with age. According to audiogram shape, patients were divided into 3 groups, mild ski-slope loss type (2 cases), flat loss type (3 cases), steep drop in low frequency (125-500 Hz or 125-1 000 Hz) and flat loss in high frequency (500 -8 000 Hz) type (5 cases). There were 20 different USH2A variant sites in these patients, of which 10 were never reported. The variations included 3 splice site variant: c.5572+1G>A, c.14969-2A>G, c.15297+1G>A; 3 frameshift variants: c.5548delT, c.62926296ATAAG>TA, c.7863delA; 4 missense variant: c.T3364G, c.11279G>C, c.13876C>G, c.14225C>T. Of the other 10 reported variants, 6 pathogenic ones were c.99100insT, c.187C>T, c.2797C>T, c.8559-2A>G, c.11156G>A, c.1510415105del. Two patients carried USH2A c.99100insT, accounting for 20% of the total variants, and the remaining variants were all detected in different patients. Of the 22 USH2A variant sites, 3 were located in exon 2. Conclusion We find 10 novel USH2A variants in 10 patients with hearing loss. In this cohort, c.99100insT is more common, and the hearing loss are more likely to be moderate to severe. Half patients are classified as low frequency steep drop and medium to high frequency flat type by audiogram shape. These findings provide clinical evidences for early diagnosis, early intervention and precise genetic counseling of USH2A.

     

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