Hb I-Toulouse in Association with Homozygosity for the α3.7 Deletion in a Pacific Island Woman

Abstract

Only four cases of Hb I-Toulouse have been reported to date. Current literature associates Hb I-Toulouse in the heterozygote with a mild chronic hemolytic anemia. The variant is mildly unstable with a tendency to form metHb. The quantity of the variant in heterozygotes has been reported as varying between 33 to 40%. This report confirms the finding from a single case, that a reduced percentage of Hb IToulouse along with microcytosis can be attributed to the co-inheritance of an abnormal α globin genotype. This current case was found in a woman of Pacific People ethnicity residing in New Zealand. There is a high prevalence of α thalassemia in this ethnic group and New Zealand has the highest Pacific population in the world. Therefore, if a reduced percentage of Hb I-Toulouse is found with microcytosis and normal iron studies, co-inheritance with α thalassemia should be considered.