病例1：患儿男，19 d，因纳差、少动2周，加重伴反应差3 d就诊。生后5 d出现纳差，反应差，住院发现血氨升高，血小板下降，全基因组遗传分析报告检测PCCA基因存在1个致病的纯合突变NM-000282.4：c.1834-1835del（p.Arg612AspfsTer44），确诊为丙酸血症。病例2：患儿男，4 d，因生后反应差、吃奶差4 d，发现血氨升高1 d就诊。生后吸吮力弱，反应逐渐变差，血氨>200 μmol/L，MMUT基因存在2个杂合变异：NM_000255.4：c.1677-1G>A，NM_000255.4：ex.5del，甲基丙二酸血症诊断明确。病例3：患儿男，20 d，因吃奶欠佳15 d，发现皮肤出血点8 d就诊，生后5 d逐渐出现喂养困难，12 d发现下肢出血点，血氨551.6 μmol/L，PCCA基因发现2个杂合变异，NM_000282.4：c.1118T>A（p.Met373Lys），NM_000282.4：ex.16-18del，确诊为丙酸血症。前2例患儿分别在持续性血液透析滤过30 h、20 h后使用卡谷氨酸；第3例患儿直接口服卡谷氨酸，未用持续性血液透析滤过，6 h内血氨从551.6 μmol/L降至72.0 μmol/L，下降速度约20~25 μmol/（kg·h），血氨下降速度与前2例相近。卡谷氨酸在3例患儿中疗效确切，未来有望优化有机酸血症的治疗方案。

Case 1: A 19-day-old male infant presented with poor feeding and decreased activity for 2 weeks, worsening with poor responsiveness for 3 days. At 5 days old, he developed poor feeding and poor responsiveness, was hospitalized, and was found to have elevated blood ammonia and thrombocytopenia. Whole-genome genetic analysis revealed a pathogenic homozygous mutation in the PCCA gene, NM-000282.4: c.1834-1835del (p.Arg612AspfsTer44), leading to a diagnosis of propionic acidemia. Case 2: A 4-day-old male infant presented with poor responsiveness and feeding difficulties since birth, with elevated blood ammonia for 1 day. He showed weak sucking and deteriorating responsiveness, with blood ammonia >200 µmol/L. Genetic testing identified two heterozygous mutations in the MMUT gene: NM_000255.4: c.1677-1G>A and NM_000255.4: ex.5del, confirming methylmalonic acidemia. Case 3: A 20-day-old male infant presented with poor feeding for 15 days and skin petechiae for 8 days. He developed feeding difficulties at 5 days old and lower limb petechiae at 12 days old, with blood ammonia measured at 551.6 µmol/L. Genetic analysis found two heterozygous mutations in the PCCA gene: NM_000282.4: c.1118T>A (p.Met373Lys) and NM_000282.4: ex.16-18del, confirming propionic acidemia. In the first two cases, continuous hemodiafiltration was performed for 30 hours and 20 hours, respectively, before administering carglumic acid. In the third case, carglumic acid was administered orally without continuous hemodiafiltration, resulting in a decrease in blood ammonia from 551.6 µmol/L to 72.0 µmol/L within 6 hours, with a reduction rate of approximately 20-25 µmol/(kg·h), similar to the first two cases. Carglumic acid was effective in all three cases, suggesting it may help optimize future treatment protocols for organic acidemia.