血红蛋白Santa Ana患儿1例的遗传学分析

Genetic analysis of a child with hemoglobin Santa Ana

目的对1例血红蛋白Santa Ana(Hb Santa Ana)患儿进行遗传学分析,明确其致病原因。方法选择2013年8月4日因"发现贫血、脾大伴尿色加深5年"于重庆医科大学附属儿童医院就诊的一例Hb Santa Ana患儿为研究对象,并收集其临床资料。采集患儿及其父母的外周血样,进行血常规检查。采用全自动血细胞分析仪检测患儿及其父母的红细胞参数,利用高效液相色谱分析(HPLC)技术检测患儿及其父母的血红蛋白组分,利用跨越断裂点PCR及PCR-反向斑点杂交技术检测患儿的常见地中海贫血基因突变,利用二代测序(NGS)检测患儿的珠蛋白基因变异,并通过Sanger测序对候选变异进行验证。结果患儿表现为轻中度溶血性贫血,血常规提示血红蛋白含量(90 g/L)和红细胞平均血红蛋白浓度(267 g/L)均偏低,网织红细胞比值(0.141)偏高,提示为低色素性增生性贫血。血红蛋白组分分析提示患儿血红蛋白F升高至10.7%,提示β珠蛋白肽链合成存在异常。患儿HPLC分析图谱可见异常峰,面积占总面积的4.5%。患儿父母的血常规和血红蛋白组分分析结果均未见异常。未在患儿中检出中国人常见的地中海贫血基因变异,珠蛋白基因测序结果提示患儿存在HBB:c.266T>C杂合变异,其父母未见相同的变异。依据美国医学遗传学与基因组学学会相关指南判定为致病变异。结论患儿存在HBB:c.266T>C杂合变异,以溶血性贫血为主要临床表征,可确诊为Hb Santa Ana。

Objective To explore the genetic basis for a child with Hemoglobin Santa Ana(Hb Santa Ana).Methods The child was admitted to the Children′s Hospital of Chongqing Medical University on August 4,2013 due to anemia,splenomegaly and deepening urine color for 5 years.His clinical data were collected.Peripheral blood samples of the child and his parents were collected for routine blood test.The erythrocyte parameters of the child and his parents were detected with an automatic hemocyte analyzer.The hemoglobin components of the child and his parents were detected by high-performance liquid chromatography(HPLC).Common mutations associated with thalassemia were detected by Gap-PCR and PCR-reverse dot blotting(PCR-RDB).Rare variants of the globin genes were detected by next generation sequencing(NGS),and the result was verified by Sanger sequencing.Results The child has shown mild to moderate hemolytic anemia.Routine blood test showed that he had lower hemoglobin(90 g/L)and mean corpuscular hemoglobin concentration(267 g/L)but a higher reticulocyte ratio(0.141),which indicated hyperplastic hypochromic anemia.Analysis of hemoglobin component showed that his hemoglobin F was elevated to 10.7%,which indicated abnormal synthesis ofβglobin peptide chain.HPLC analysis showed an abnormal peak accounting for 4.5%of the total area.Neither of his parents was found to have abnormal results by routine blood test and hemoglobin component analysis.No common globin gene variant was detected in the child.Gene sequencing revealed that the child has harbored a heterozygous variant of HBB:c.266T>C,which was de novo in origin.Based on the guidelines of American College of Medical Genetics and Genomics,the variant was predicted to be pathogenic.Conclusion The heterozygous HBB:c.266T>C variant probably underlay the hemolytic anemia associated with Hb Santa Ana in this patient.