异戊酸血症2例患儿的临床研究并文献复习

Clinical and genetic analysis of two Chinese patients with isovaleric acidemia and review of literature

目的 探讨异戊酸血症（IVA）患儿的临床特点和诊治经验,以及异戊酰辅酶A脱氢酶（IVD）基因突变情况,以提高认识,更好地预防和治疗该病.方法 分析2例IVA同胞患儿的临床病史及实验室检查,并对患儿及双亲IVD基因12个外显子及内含子进行扩增,聚合酶链反应（PCR）产物直接测序,分析基因突变结果并进行相关文献复习.结果 2例同胞患儿均诊断为IVA,哥哥新生儿期急性起病,伴高氨血症,低钙血症,全血细胞减少;弟弟无明显临床症状但血氨升高,2例患儿尿有机酸分析均显示尿中检出大量异戊酰甘氨酸.哥哥因脓毒症及出血于新生儿期夭折;弟弟治疗及时并随访2年病情控制佳.IVD基因测序显示,在第10号外显子上,2例患儿及母亲存在杂合突变：c.1016G＞ A（C339Y）,该突变以往未见报道,父亲以及50例健康对照组未见突变.国内详细报道的总共15例IVA患儿中有11例新生儿期发病,12例呈现典型IVA表现,12例表现出特殊体味,9例全血细胞减少,5例高氨血症,6例低钙血症,6例报道死亡,5例通过饮食控制病情有不同程度的好转,存活患儿仅2例随访超过2年.结论 新报道2例IVA患儿,同时发现1个新的IVD基因突变,即C339Y突变,该突变可能引起IVD蛋白结构和功能的改变.同时,直接基因测序不能识别出所有的IVA患者,基因诊断的漏诊需要引起临床医师的注意.IVA近年来报道有增多的趋势.

Objective To discuss the clinical features and treatment of isovaleric academia （IVA） patients,and to gain more comprehensive understanding of isovaleryl-CoA dehydrogenase（IVD） mutation in 2 siblings in order to raise awareness to prevent the occurrence of IVA.Methods The clinical history and laboratory test of 2 cases of children with IVA were carried out.The exons and neighboring introns of IVD gene of the whole family were PCR-amplified for DNA sequencing.The literature review of IVA in China was also conducted.Results Organic acid analysis of urine by GC/MS for both siblings showed extremely elevated concentrations of isovaleric glycine.For the older sibling,an acute episode of IVA caused severe metabolic stress and eventually death in the neonatal period.However,the disease was well-controlled for the younger sibling due to timely treatment and follow-up care for 2 years.The DNA sequencing of the IVD gene in the family revealed a novel c.1016G 〉 A（C339Y） heterozygous mutation in mother and both of the siblings.No IVD mutation was detected in father or in any of the 50 cases of healthy controls.According to literature review,15 cases of IVA were reported in recent 15 years in China,including neonatal onset （11 cases）,acute episode （12 cases）,odor of sweaty feet （12 cases）,pancytopenia （9 cases）,hyperammonemia （5 cases）,hypocalcemia （6 cases）,and 6 cases of death were reported.Additionally,5 cases that received treatment of BCAA-free formula milk showed positive outcome.However,only 2 cases were followed up for more than 2 years.Conclusions Two new IVA patients carrying c.1016G 〉 A（C339Y） mutation were reported in China.The mutation may lead to conformational change and functional deficient of the IVD protein.It is also necessary to point out that using direct DNA sequencing can not identify all patients with IVA due to limitations of this technology,and thus clinicians should be aware of the possibility of genetic misdiagnosis.Moreover,there is a trend of increasing IVA in China in recent years.