COMPOUND HETEROZYGOSITY FOR α⁰-THALASSEMIA (−−^THAI) AND Hb CONSTANT SPRING CAUSES SEVERE Hb H DISEASE

Abstract

We report two unrelated cases of Hb H-Constant Spring (Hb H-CS) disease caused by a compound heterozygosity for α⁰-thalassemia (−−^THAI deletion) and Hb CS (α142, TAA→CAA) in Thai patients. Hematological and clinical observations in the probands are more severe than those of deletional type of Hb H disease (−−/–α), owing to an early onset of anemia and recurrent episode of anemic crises. These cases also address the importance of the −−^THAI deletion which causes a severe clinical phenotype, and that could be missed by routine screening. We suggest that testing for this mutation should be included in the screening program for the prevention and control of thalassemia in Thailand, and possibly in other countries in Southeast Asia, where α⁰-thalassemias are highly prevalent.