目的 总结3例腺苷脱氨酶2(ADA2）缺乏症患儿的临床特征及基因型特点，提高对该病的认识。方法 回顾性分析3例ADA2缺乏症患儿的临床特点并利用全外显子测序进行遗传学分析。利用试剂盒测定患儿血浆中ADA2酶的活性。总结该病的临床及基因型特征。结果 本组3例患儿均存在ADA2基因变异，例1以反复发热、皮疹、惊厥为主要临床表现，合并脑卒中，伴炎症指标明显升高，ADA2基因存在复合杂合变异：c.139G>T和c.484T>C突变。例2以反复发热、皮疹为主要临床表现，病程中合并消化道穿孔、脑卒中，炎症指标明显升高。WES检测发现ADA2基因存在c.916C>T及c.1069G>A复合杂合突变。例3以反复发热、咳嗽为主要临床表现，合并心肌炎，伴免疫功能明显下降；WES检测发现患者ADA2基因存在c.849T>G纯合突变。血浆ADA2酶活性测定发现例1和2酶活性显著降低。结论 ADA2缺乏症国内罕见，临床特征多变，掌握其临床特征及基因特点，有助于提高诊断水平。

Objective To summarise the clinical features and genotypic characteristics of three children with adenosine deaminase 2 (ADA2) deficiency and to improve understanding of the disease. Methods The clinical features of three children with ADA2 deficiency were retrospectively analysed and genetically analysed using exome sequencing (ES). The activity of ADA2 enzyme in the plasma of the patients was measured using a kit. The clinical and genotypic features of the disease were summarised. Results All three children in our group had ADA2 gene variants. Case 1 had recurrent fever, rash, and convulsions as the main clinical manifestations, combined with stroke, accompanied by markedly elevated inflammatory indexes, and there were compound heterozygous variants in the ADA2 gene: c.139G>T and c.484T>C variants. Case 2 had recurrent fever and rash as the main clinical manifestations, combined with gastrointestinal perforation and stroke during the course of the disease, with markedly elevated inflammatory indexes. ES identified compound heterozygous variants of c.916C>T and c.1069G>A in the ADA2 gene. In Case 3, the patient had recurrent fever and cough as the main clinical manifestations, combined with myocarditis, accompanied by markedly reduced immune function. ES identified c.849T>G homozygous variants in ADA2 gene; Plasma ADA2 enzyme activity was found to be significantly reduced in case 1 and 2. Conclusion ADA2 deficiency is rare in China, with variable clinical features, and mastering its clinical features and genetic characteristics can help improve the diagnosis level.