Wilson病双（多）胞胎家系的临床和基因突变研究

Clinical and genetic study of Wiison＇s disease in affected twins and siblings

目的观察双（多）胞胎Wilson病家系的临床和基因突变特点。方法收集双（多）胞胎Wilson病家系的临床资料，留取其全血标本，提取基因组DNA，应用短串联重复（shorttandemrepeats，STR）分型判定双胞胎是否为同卵双生，用DNA测序法检测ATP7B基因各外显子的突变。结果5个双胞胎家系的患者均符合Wilson病的诊断标准。STR分型提示4个家系为同卵双生，1个家系为异卵双生。3个双胞胎家系的患者均以肝症状起病，另外2个家系的患者以脑症状起病。在4个家系的患者中检出ATP7B基因的突变，均位于第8和（或）第13外显子，其中1个家系的患者同时携带第8外显子P．R778W杂合突变和第13外显子P．P992L纯合突变，其父母分别为P．R778w杂合突变和P．P992L杂合突变的携带者，因此该家系的患者发生了杂合丢失现象。有1个家系的2例患者及其父母亲各外显子均未检出突变。1个三胞胎家系中的1名女性成员为脑症状起病的Wilson病患者，1名男性为无症状的亚临床型Wilson病患者，另1例女性成员未患病，这3位成员及其母亲均检出第13外显子P．P992L杂合突变。结论本研究结果进一步证实了遗传因素在Wilson病发病中的主要作用。杂合丢失现象是除点突变外Wilson病的另一种发病机制。

Objective To study the clinical and genetic characteristics of twins and siblings affected with Wilson＇s disease （WD）. Methods Clinical data and blood samples were collected from the subjects after informed consent was obtained. Genomic DNA was extracted and potential mutations in the exons in A TPTB gene were detected with PCR-DNA sequencing. Short tandem repeat （STR） genotyping was performed to determine the zygosity of the twins. Results The 5 pairs of twins have all met the diagnostic criteria for WD. STR genotyping has confirmed that 4 pairs were monozygotic twins. 3 pairs of twins had an onset with liver symptoms, the other 2 had an onset with brain symptoms. ATP7B gene mutations were detected in 4 pairs of twins, which have all located in exons 8 and 13. A heterozygous p. R778W mutation in exon 8 and homozygous p. P992L mutation in exon 13 were detected in all patients from one family, whose parents have carried a heterozygous p. R778W mutation and p. P992L heterozygous mutation, respectively, which suggested loss of heterozygosity （LOH）. In one family, no mutation was detected in all exons of the ATPTB gene in the patients and their parents. For a triplet, one female was with definite WD and brain symptoms at the onset, one male had subclinical type with WD, whilst another female was completely normal. The triplets and their mother have all carried a p. P992L heterozygous mutation. Conclusion Above results have confirmed an important role for genetic factors in the pathogenesis of WD. In addition to point mutations, LOH is also involved in the pathogenesis for WD.