Molecular basis and hematological characterization of Hb H disease in Southeast Asia

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Abstract
We molecularly characterized sixty‐seven cases of Hb H disease by the polymerase chain reaction. The strategy depends on amplifying the α‐thalassemia‐1 (α‐thal‐1) gene by prlmers flanking the breakpoint and sequence differences of the 3′ end of the α‐globin gene and the nonhomologous elements I, II, and III among different types of α‐thala‐2. In the 67 cases studied, all involved α‐thal‐1 of the Southeast Asia type (SEA) In combination with deletional or nondeletional α‐thal‐2. Thirty‐two cases were of the deletion form and 35 cases were of the nondeletion form. In 32 cases of the deletion form, 29 cases were rightward deletion (‐α3.7), and three cases were leftward deletion (‐α4.2). We found that all of the nondeletion forms were α‐thal‐1 of SEA type with Hb CS. After the subtyping of Hb H with ‐α3.7, 26 out of 29 were type I deletion and 3 out of 29 were type II deletion. Comparlsons of clinical data of deletion forms and the nondeletion form showed that there were earlier occurrence of anemic symptoms and a larger erythrocyte volume in the nondeletion form group (P < 0.005).