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Complex interactions between thalassemia defective alleles compromise screening and cause severe anemia in a Chinese family

Sir, in normal individuals (αα/αα; βA/βA), the amount of αglobin chains produced by α genes is comparable to that of βglobin chains produced by β genes. Thalassemia results when defects of the α or β genes occur. The clinical phenotype arises from both the diminished amount of the particular globin chains and from the resultant chain imbalance that is due to the normal production of the partner chains.1 The more severe the α/β imbalance, the more severe the ineffective erythropoiesis and anemia. In clinical practice, the prevention of thalassemia is achieved by prepregnancy screening of the couples, followed by prenatal diagnosis of the atrisk families. The screening begins with using an electronic bloodcell counter to provide erythrocyte indices. Individuals with hypochromic microcytosis (MCV<80 fl or MCH<27 pg) are designated as screeningpositive and are investigated further to determine the defects of the α or β genes. Those with normal erythrocyte indices are regarded as screeningnegative, with low risk of giving birth to a child affected with severe thalassemia syndromes. However, this screening strategy has pitfalls as defective alleles can be overlooked by the normal erythrocyte indices presentation. Here, we report on such a Chinese family.