Diagnosis: α-Thalassemia trait
• There are four α-globin genes (two on each chromosome) with two α-globin genes in cis on each chromosome (α2, α1). α-Thalassemias are most commonly caused by deletion of one or more α-globin genes.
• α-Thalassemia trait can be inherited as one α-globin gene deletion (-α/αα), two α- globin gene deletions in trans (-α/-α), or two α-globin genes deleted in cis (--/αα).
• One α-globin gene deletion --α/αα) is usually clinically and hematologically silent but can show mild microcytosis and hypochromia.
• α-Thalassemia trait caused by two gene deletions in cis or trans (--/αα or --α/-α, respectively) is hematologically mild; there may be a very mild anemia, but the hemoglobin can have overlap with the reference range; and an elevated red blood cell count (RBC), a reduced mean corpuscular volume (MCV), and a reduced mean corpuscular hemoglobin (MCH) are generally present.
• A presumptive diagnosis of α-thalassemia trait can be made when there are red cell indices suggestive of thalassemia (i.e., elevated RBC; low MCV and MCH), a normal hemoglobin A2 and F, and normal iron studies.
