Abstract: Objective    To investigate the prevalence， clinical and gene mutation characteristics of primary carnitine deficiency（PCD） in Beijing， in order to provide basis for disease diagnosis， treatment and genetic counseling. Methods  The free carnitine and acylcarnitine levels in the blood of 243，898 neonates in Beijing from January 2017 to July 2023 were measured by tandem mass spectrometry（MS/MS）. The clinical， biochemical and gene mutation characteristics of patients with PCD were analyzed. The symptomatic treatment was given and the growth and development were followed up. Results    Among 243，898 live births， 1561 had decreased free carnitine （C0） concentration in initial screeing and 1345 were recalled.Ten cases of PCD were diagnosed and the incidence of PCD was 4.1/100， 000 （1/24， 390） . Six cases of maternal PCD were confirmed. No abnormal clinical manifestations were found in all 10 patients. There was decrease in both blood C0 and multiple acylcarnitine levels. Eight mutations were detected in the SLC22A5 gene of nine patients， including 7 types of reported mutations and 1 novel mutation，with c.1400C>G（p.S467C） as the hot spot mutation，of which three patients showed homozygous mutation，all being c.1400C>G（p.S467C）， and the rest were compound heterozygous mutations. The median follow-up age of 9 patients was 8（5，20）months， and no clinical symptoms were observed. Their growth and development were normal. Conclusion    The prevalence of PCD in Beijing is 1/24，390.c.1400C>G （p.S467C） is the hot spot mutation in PCD patients in Beijing. Patients with PCD confirmed through neonatal screening have no obvious clinical symptoms， but it is necessary to have long-term standardized treatment and follow-up .

Key words: primary carnitine deficiency, free carnitine, gene mutation, tandem mass spectr-ometry, neonatal screening

摘要： 目的    分析北京市原发性肉碱缺乏症（primary carnitine deficiency，PCD）患儿的发病率、临床特征及基因突变特点，为该疾病的诊断、治疗和遗传咨询提供依据。方法    采用串联质谱技术检测2017年 1月至 2023年7月北京市243，898名新生儿干血滤纸片中游离肉碱（free carnitine，C0）和酰基肉碱水平，对确诊PCD患儿进行临床、生化及基因突变特点分析，对症治疗并随访生长发育情况。结果    243，898名活产新生儿中初筛C0浓度下降1561名，召回1345名新生儿，确诊PCD患儿10例，PCD发病率为4.1/10万（1/24，390）；确诊母源性PCD患者6例。10例确诊患儿均无异常临床表现，血C0均下降伴多种酰基肉碱水平下降。9例患儿行SLC22A5基因检测到8种变异，包括7种已报道突变和1种新变异，以c.1400C>G（p.S467C）为主，其中3例患儿为纯合变异，均为c.1400C>G（p.S467C），6例为复合杂合变异。9例患儿随访中位年龄为8（5，20）月龄，均未出现临床症状，生长发育正常。结论    北京市新生儿PCD发病率为1/24，390，c.1400C>G（p.S467C）是北京市PCD患儿的热点突变类型；新生儿筛查确诊的PCD患儿无明显临床症状，但需要长期规范治疗与随访。

关键词: 原发性肉碱缺乏症, 游离肉碱, 基因突变, 串联质谱分析, 新生儿筛查