双基因突变型X连锁Alport综合征女性患者临床与遗传学特征分析

Clinical and genetic characteristics of female X-linked Alport syndrome with digenic mutations

目的X连锁Alport综合征(X-linked Alport syndrome,XLAS)女性患者存在较强的临床异质性。本研究旨在通过分析并总结COL4A3、COL4A4、COL4A5双基因突变型XLAS女性患者的临床表型和基因突变的特征,以提高对此类多基因遗传XLAS女性患者疾病特点的认识。方法回顾性分析2019年1月—2020年12月于上海交通大学医学院附属新华医院肾脏科经全外显子组测序明确诊断为COL4A3、COL4A4、COL4A5双基因突变型XLAS的3例女性患者的临床和基因突变特点。通过家系内调查和Sanger测序明确上述患者的家系内患病成员及其所携带COL4A3、COL4A4、COL4A5基因突变情况,并比较携带COL4A3、COL4A4、COL4A5双基因突变与单基因突变患者的临床表型及其肾脏预后。搜索数据库,整理和归纳总结10例COL4A3、COL4A4、COL4A5双基因或三基因突变型XLAS女性患者的临床和基因突变特点。结果3例COL4A3、COL4A4、COL4A5双基因突变型XLAS女性患者中,1例同时携带COL4A3和COL4A5基因杂合突变,2例同时携带COL4A4和COL4A5基因杂合突变。总共发现6种COL4A3、COL4A4、COL4A5基因突变,均为错义突变。3例患者均有血尿和不同程度的蛋白尿,其中1例于40岁时进展至终末期肾病。1例行肾脏活组织检查,但未见肾小球基底膜明显异常,Ⅳ型胶原α3、α5染色呈阳性。3例患者均无肾外表现。家系内调查发现9例家系内患病成员,其中7例经Sanger测序验证为携带COL4A3、COL4A4、COL4A5单基因突变。与家系内仅携带COL4A5突变的XLAS女性患病成员相比,COL4A3、COL4A4、COL4A5双基因突变型XLAS女性患者发病早,易合并蛋白尿和肾功能受损。10例经检索数据库获得的女性患者中,6例患者携带COL4A3和COL4A5双基因杂合突变,3例患者携带COL4A4和COL4A5双基因杂合突变,1例患者同时携带COL4A3、COL4A4和COL4A5三基因杂合突变;2例患者分别于40、44岁进展至终末期肾病;3例患者合并肾外表现。结论多基因遗传是影响XLAS女性患者临床异质性的重要因素。对发病较早、临床表现较严重的XLAS女性患者,需考虑存在COL4A3、COL4A4、COL4A5多基因遗传可能,并运用二代测序技术予以明确。

Objective There is strong clinical heterogeneity in female patients with X-linked Alport syndrome(XLAS).The aim of the study is to analyze and summarize the clinical phenotypes and genetic characteristics of female XLAS patients with COL4A3,COL4A4 and COL4A5 digenic mutations and to improve the understanding of this disease features.Methods Clinical and genetic mutation characteristics of 3 female XLAS patients with digenic COL4A3,COL4A4,and COL4A5 mutations diagnosed between January 2019 and December 2020 in Shanghai Xinhua Hospital were retrospectively analyzed.COL4A3,COL4A4,and COL4A5 were simultaneously sequenced in these patients by whole exome sequencing(WES).Family investigation and Sanger sequencing were used to identify affected relatives.Clinical manifestations and renal prognosis were compared between patients with COL4A3,COL4A4 and COL4A5 digenic mutations and single mutation.Meanwhile,we searched databases and summarized the clinical and gene mutation characteristics of 10 female XLAS patients with COL4A3,COL4A4 and COL4A5 digenic or trigenic mutations.Results COL4A3 and COL4A5 heterozygous mutations were detected in 1 patient,and COL4A4 and COL4A5 heterozygous mutations were found in the other 2 patients.All the six heterozygous COL4A3,COL4A4 and COL4A5 mutations were missense mutations.All the 3 patients developed proteinuria alongside hematuria and 1 patient progressed into end-stage renal disease(ESRD)at the age of 40.One patient underwent renal biopsy,no obvious abnormality was found in glomerular basement membrane(GBM),and collagen typeⅣα3 andα5 immunostaining were both positive.None of the patients had extra-renal manifestations.Family investigation found 9 affected relatives(7 genetically diagnosed as COL4A3,COL4A4 and COL4A5 single gene mutation).Compared with the family member with only COL4A5 mutation,female XLAS patients with COL4A3,COL4A4 and COL4A5 digenic mutations had earlier onset,and were more likely to have proteinuria and renal dysfunction.In the 10 patients obtained from databases,6 carried COL4A3 and COL4A5 heterozygous mutations,3 had COL4A4 and COL4A5 heterozygous mutations,and 1 had COL4A3,COL4A4 and COL4A5 heterozygous mutations.Two of them progressed to ESRD at the age of 40 and 44,respectively,and extrarenal manifestations were found in 3 of them.Conclusion Polygenic inheritance can help explain the heterogeneity of renal phenotype in XLAS female patients.Digenic inheritance of COL4A3,COL4A4 and COL4A5 mutations should be considered once female XLAS patients presented with severe clinical phenotype and early onset.Next generation sequencing(NGS)can unbiasedly detect all mutations in these patients and make a correct diagnosis.