目的:提高对先天性铁粒母细胞性贫血(CSA)发病机制及治疗的认识。
方法:检测先证者和其他家族成员的全血细胞计数和铁代谢。使用来自家族成员的基因组DNA作为模板,通过普通聚合酶链反应(PCR)对ALAS2基因的完整编码区进行突变分析。通过直接测序检测ALAS2突变,并且通过测序随后进行质粒克隆来确认突变类型。
结果:先证者男性表现为小细胞性低色素性贫血(血红蛋白84g/L,平均红细胞体积64fL,平均红细胞血红蛋白16.5pg),和铁过载(血清铁44.7μmol/L,血清铁蛋白3123μg/L和转铁蛋白饱和度0.84)。在先证者和来自该家族的3名雌性中鉴定出预测Lys156Glu氨基酸变化的突变466A>G。先证者为该突变的半合子,并表现为小红细胞性贫血和铁超负荷,而所有3个杂合雌性显示红细胞分布宽度略有增加,没有任何其他症状。先证者每天服用300毫克吡哆醇,并与去铁胺进行铁螯合治疗一年,患者的造血功能得到了持久的改善。包括血红蛋白增加到98g/L,血清铁蛋白减少到1580μg/L。
结论:这是在中国3代系中鉴定的ALAS2基因中的一个新的K156E替换。我们的发现强调了基于基因的CSA诊断的重要性,ALAS2突变的CSA患者对吡哆醇治疗有反应。
OBJECTIVE: To raise awareness of molecular pathogenesis and treatment of congenital sideroblastic anemia (CSA).
METHODS: A complete blood count and iron metabolism were detected from the proband and other members of the family. Mutation analysis was performed on the complete coding regions of ALAS2 gene by common polymerase chain reaction (PCR) using genomic DNA as a template from members the family. ALAS2 mutations were detected by direct sequencing and mutation types were confirmed by sequencing followed by plasmid cloning.
RESULTS: The proband male presented with microcytic hypochromic anemia (hemoglobin 84 g/L, mean corpuscular volume 64 fL, mean corpuscular hemoglobin 16.5 pg), and iron overload (serum iron 44.7 μmol/L, serum ferritin 3 123 μg/L and transferrin saturation 0.84). A mutation 466 A>G predicting a Lys156Glu amino acid change was identified in the proband and 3 females from the family. The proband was hemizygous for this mutation and presented with microcytic anemia and iron overload, while all 3 heterozygous females showed marginally increased red cell distribution width without any other symptoms. The proband treated with 300 mg of pyridoxine per day and iron chelation therapy with deferoxamine for one year had durable hematopoietic patients improvements, including increase in hemoglobin to 98 g/L and decrease in serum ferritin to 1 580 μg/L.
CONCLUSIONS: This was a novel K156E substitution in ALAS2 gene identified in a 3-generation pedigree in China. Our findings emphasized the importance of gene based diagnosis of CSA, and CSA patient with ALAS2 mutation responded to pyridoxine treatment.