The molecular and hematological heterogeneity of alpha thalassemia

A study of genotypes in alpha thalassemia and their corresponding hematological phenotypes has shown that alpha(+) thalassemia is the most frequent type encountered in a Sydney population. Phenotypes of heterozygous alpha(+) thalassemia (alpha alpha/-alpha) in adults or children differ little from normal and so the disorder is difficult to identify. In contrast, Hb Bart's (gamma 4) is a useful marker for alpha alpha/-alpha in cord blood samples. Abnormal phenotypes are present in homozygous alpha(+) thalassemia (-alpha/-alpha), heterozygous alpha(0) thalassemia (alpha alpha/--) and non-deletional alpha thalassemia. Therefore, detection by routine hematological studies should be possible. A less severe phenotype in -alpha/-alpha compared to alpha alpha/-- was found which is interesting since 2 alpha globin genes are lost in both instances.