目的　了解PI3K-δ过度活化综合征的临床特征及致病基因。 方法　回顾分析1例PI3K-δ过度活化综合征 患儿的临床资料。结果　患儿，男， 3岁10个月，反复呼吸道感染，肝脾肿大，发育落后。提取患儿及父母外周血DNA，通 过全外显子组测序及Sanger验证，证实患儿PIK3CD基因存在错义变异c.3061G>A（E1021K），先证者父母PIK3CD基因 均未发现上述变异，为新生变异。该突变使PIK3CD基因发生功能获得性突变，导致编码的p110δ活性增强，PI3K-PIP3AKT-mTOR信号通路过度激活，诱导细胞分化增殖，致疾病发生，为致病性突变。结论　PI3K-δ过度活化综合征为罕见 的常染色体显性遗传免疫缺陷病，基因检测可协助诊断。

　Objective　To explore the clinical characteristics and pathogenic genes of activated PI3K-δ syndrome (APDS). Method 　The clinical data of APDS in a child was retrospectively analyzed. Results　A boy aged 3 years and 9 months presented recurrent respiratory infections, hepatosplenomegaly and growth retardation. The DNA was extracted from the peripheral blood of the child and his parents. The sequence analyses were performed by whole exome sequencing technology and the mutant gene was validated by Sanger sequencing. A novel heterozygous missense mutation (De novo), c.3061G>A (E1021K), was found in the PIK3CD gene in the child, and both his parents had normal genotypes. PIK3CD gain-of-function mutations leads to enhanced activity of the encoded p110δ. The PI3K-PIP3-AKT-mTOR signaling pathway is over-activated, which induces cell differentiation and proliferation, and thus the disease is caused. So the mutation is a pathogenic mutation. Conclusion　PI3K-δ overactivation syndrome is a rare autosomal dominant immunodeficiency disease, and genetic testing can assist the diagnosis.