Thalassemia intermedia as a result of heterozygosis for β0-thalassemia and αααanti-3.7/αα genotype in a Brazilian patient

Abstract

We report a case in which the interaction of heterozygosis for both the β0-IVS-II-1 (G→A) mutation and the αααanti-3.7 allele was the probable cause for the clinical occurrence of thalassemia intermedia. The propositus, a 6-year-old Caucasian Brazilian boy of Portuguese descent, showed a moderately severe chronic anemia in spite of having the β-thalassemia trait. Investigation of the α-globin gene status revealed heterozygosis for α-gene triplication (ααα/αα). The patient's father, also presenting mild microcytic and hypochromic anemia, had the same α and β genotypes as his son, while the mother, not related to the father and hematologically normal, was also a carrier of the αααanti-3.7 allele. The present case emphasizes the need for considering the possibility of α-gene triplication in β-thalassemia heterozygotes who display an unexpected severe phenotype. The β-thalassemia mutation found here is being described for the first time in Brazil.