Alagille综合征患儿1例临床和遗传学分析:一个包含JAG1基因的染色体新中间缺失的识别

Clinical and genetic study of an infant with Alagille syndrome: identification of a novel chromosomal interstitial deletion including JAG1 gene

Alagille综合征(ALGS)是一种常染色体显性遗传病,可累及肝脏、心脏、骨骼、眼睛、肾脏、颜面等多个系统。本文报道1例ALGS患儿的临床和遗传学特征。患儿为3个月10d男婴,因发现皮肤、巩膜黄染3个月就诊。体格检查示:宽额头,小下颌;胸骨左缘第2、3肋间可闻及3~4/6级收缩期杂音;腹部膨隆,肝右肋下3cm可触及,质地中等。生化结果示肝功能明显异常,胆红素升高,且以结合胆红素升高为主,伴总胆汁酸和γ-谷氨酰转肽酶显著升高。心脏彩超示房间隔缺损、肺动脉狭窄。二代测序发现该患儿JAG1基因整体杂合缺失,而染色体微阵列分析在患儿20号染色体p12.3p12.2处检出约3.0Mb缺失,该范围包含ALGS致病基因JAG1。该患儿具备特殊面容、心脏畸形和胆汁淤积等临床表现,结合遗传学分析结果,诊断ALGS明确。确诊后给予对症支持治疗,现已随访至生后11个月,胆红素较治疗前明显下降,但总胆汁酸和γ-谷氨酰转肽酶等指标仍明显升高,其远期预后仍有待随访观察。本研究扩展了JAG1基因突变谱,同时为患儿诊断、治疗及家系遗传咨询和产前诊断提供了实验室依据。

Alagille syndrome（ALGS） is an autosomal dominant disease affecting multiple systems including the liver, heart, skeleton, eyes, kidneys and face. This paper reports the clinical and genetic features of an infant with this disease. A 3-month-and-10-day-old female infant was referred to the hospital with jaundiced skin and sclera for 3 months. Physical examination revealed wide forehead and micromandible. A systolic murmur of grade 3-4/6 was heard between the 2th and 3th intercostal spaces on the left side of the sternum. The abdomen was distended, and the liver palpable 3 cm under the right subcostal margin with a medium texture. Serum biochemistry analysis revealed abnormal liver function indices, with markedly elevated bilirubin（predominantly direct bilirubin）, total bile acids（TBA） and gamma-glutamyl transpeptidase（GGT）. Atrial septal defect and pulmonary stenosis were detected on echocardiography. Next generation sequencing detected entire deletion of the JAG1 gene, and then chromosomal microarray analysis revealed a novel interstitial deletion of 3.0 Mb in size on chr20p12.3p12.2, involving JAG1 gene. The child had special facial features, heart malformations, and cholestasis, and based on the genetic findings, ALGS was definitively diagnosed. Thereafter, symptomatic and supportive treatment was introduced. Thus far, the infant had been followed up till his age of 11 months. The hyperbilirubinemia got improved, but GGT and TBA were persistently elevated, and the long-term outcome needs to be observed. This study extended the JAG1 mutation spectrum, and provided laboratory evidences for the diagnosis and treatment of the patient, and for the genetic counseling and prenatal diagnosis in the family.