目的 探讨先天性胆汁酸合成障碍2型（CBAS2）患儿血浆氨基酸谱改变及临床意义。方法 回顾性分析2016年1月至2021年6月就诊的婴儿胆汁淤积症患儿的临床资料。患儿根据病因分为CBAS2组、citrin缺陷导致的婴儿肝内胆汁淤积症（NICCD）组以及不明原因婴儿肝内胆汁淤积症（INH）组，比较三组22种血浆氨基酸的差异。结果 纳入婴儿胆汁淤积症患儿85例，男58例、女27例，中位年龄2.3（2.0~4.0）月。中位总胆红素为134.9（103.1~181.7） μmol/L，中位直接胆红素79.0（62.2~110.6） μmol/L。CBAS2组12例患儿中11例（91.7%）有≥3种氨基酸改变，11例（91.7%）支链氨基酸（BCAA，包括亮氨酸、异亮氨酸、缬氨酸）在正常范围；INH组23例患儿中17例（73.9%）有≥3种氨基酸改变；NICCD组50例患儿均有≥3种氨基酸改变。与INH组相比，CBAS2和NICCD组的天冬酰胺、丝氨酸、苏氨酸、酪氨酸水平较高；与NICCD组相比，CBAS2组谷氨酰胺、丙氨酸、色氨酸、亮氨酸、丙氨酸/瓜氨酸水平较高，瓜氨酸、精氨酸、蛋氨酸、碱性氨基酸、苏氨酸/丝氨酸水平较低，差异均有统计学意义（P<0.05）。结论 CBAS2患儿血浆氨基酸谱变化广泛。CBAS2患儿血浆氨基酸谱变化与NICCD、INH患儿不同，这对CBAS2的诊断及鉴别诊断有重要意义。

Objective To investigate the changes of plasma amino acid spectrum and its clinical significance in infants with CBAS2(congenital bile acid synthesis disorder type 2 ). Methods The clinical data of children with infantile cholestasis treated from January 2016 to June 2021 were retrospectively analyzed. According to the etiology, they were divided into CBAS2 group, neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD ) group and idiopathic neonatal intrahepatic hepatitis (INH) group. The differences of 22 amino acids in plasma among the three groups were compared. Results A total of 85 infantile cholestasis patients (58 boys and 27 girls) were included, and the median age was 2.3 (2.0-4.0) months. The median total bilirubin was 134.9 (103.1-181.7) μmol/L, and the median direct bilirubin was 79.0 (62.2-110.6) μmol/L. Among the 12 patients in CBAS2 group, 3 or more amino acids changed in 11 patients (91.7%) and branched chain amino acid (leucine, isoleucine and valine) was normal in 11 patients (91.7%). In the INH group, 17 (73.9%) of the 23 patients had≥3 amino acid changes. All the 50 patients in NICCD group had ≥3 amino acid changes. Compared with INH group, the levels of asparagine, serine, threonine and tyrosine in CBAS2 and NICCD groups were higher. Compared with NICCD group, the levels of glutamine, alanine, tryptophan, leucine and alanine/citrulline were higher, while the levels of citrulline, arginine, methionine, basic amino acid and threonine/serine were lower in CBAS2 group, and the differences were statistically significant (P<0.05). Conclusions Plasma amino acid spectra in children with CBAS2 vary widely. The changes of plasma amino acid spectra in CBAS2 children are different from those in NICCD and INH children, which is of great significance for the diagnosis and differential diagnosis of CBAS2.