Hemoglobin Ottawa (HBA2:c.46G>C) and β+ thalassemia (HBB:c.-138C>T) detected in an Indian male by capillary zone electrophoresis
Hemoglobin (Hb) Ottawa [α15(A13)Gly>Arg], also known as Hb Siam, results from GGT>CGT mutation in codon 15 of either HBA1 or HBA2. Hb Ottawa carriers typically have normal hematology but when the variant is coinherited with either α or β thalassemia, microcytic red cell indices were observed. The percentage of variant detected using routine methodology was variable (14-33%), with a higher percentage found when co-inherited with an abnormal α-globin genotype. The case presented here involved an Indian male with microcytic red cell indices, who was heterozygous for Hb Ottawa (HBA2:c.46G>C) and β+ thalassemia (HBB:c.-138C>T). This case represents the first reported finding of Hb Ottawa in the Indian population, as well as the first time capillary zone electrophoresis (CZE) has been used to identify the variant. The abnormal red cell indices were attributed to co-inheritance of β+ thalassemia mutation (HBB:c.-138C>T), which alters binding of transcriptional factors to the HBB promoter and reduces transcription from the allele. The mild β+ thalassemia mutation has commonly been found in the Indian population.
渥太华血红蛋白（Hb）[α15(A13)Gly>Arg]，又称Hb Siam，由HBA1或HBA2的第15密码子GGT>CGT突变所致。Hb渥太华携带者通常血液学正常，但当变异体与α或β地中海贫血共同遗传时，可观察到微红细胞指数。使用常规方法检测到的变异比例不一（14-33%），当与异常的α-球蛋白基因型共同遗传时，发现的变异比例更高。这里介绍的病例涉及一名印度男性，微红细胞指数，他是Hb Ottawa（HBA2:c.46G>C）和β+地中海贫血（HBB:c.-138C>T）的杂合子。该病例是印度人群中首次发现Hb Ottawa的报道，也是首次使用毛细管区电泳（CZE）来鉴定该变异。红细胞指数异常的原因是β+地中海贫血突变（HBB:c.-138C>T）的共同遗传，该突变改变了转录因子与HBB启动子的结合，减少了等位基因的转录。轻度β+地中海贫血突变常见于印度人群中。
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