Alpha Thalassemia (2)

Alpha thalassemia trait is characterized by two functional genes that code for the production of alpha globins [(-a/-a) or (--/aa)]. The two genes can either occur on the same chromosome (cis-type) or on each of the pair (trans-type). Cis-type a-thalassemia trait tends to be found in individuals of Asian descent, while trans-type tends to run in individuals of African descent. Cis-type can be co-inherited with another cis-type or hemoglobin H disease to result in alpha thalassemia major, or hydrops fetalis. Individuals who have alpha thalassemia trait are identified by microcytosis, erythrocytosis, hypochromia, and mild anemia. The diagnosis is made by a combination of family studies and the ruling out of both iron deficiency anemia and beta thalassemia trait. In the neonatal period, when hemoglobin Bart's (d⁴) is present, the diagnosis can be strongly suspected. In children, there are no markers such as Hgb A₂ and Hgb F to make the diagnosis. (One exception is the case where both of the deletions occur on the same chromosome and zeta [z] globin is expressed in carriers. This is most common in Southeast Asians.) The diagnosis is one of exclusion. The clinician should be satisfied with the presumed diagnosis if the above criteria are met. During pregnancy, the microcytic anemia can be mistaken for anemia of pregnancy.

The individual with a thalassemia trait will experience no significant health problems except a possible slight anemia which cannot be treated with iron. <next>

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