Secondary erythrocytosis caused by hemoglobin Tak/(δβ)0-thalassemia syndrome

Secondary erythrocytosis may arise from several causes, but an association with oxygen transport is rare. We describe for the first time a form of secondary erythrocytosis caused by compound heterozygosity for hemoglobin (Hb) Tak and (δβ)(0)-thalassemia found in an adult Thai individual. The patient had marked erythrocytosis and microcytosis with increased Hb and hematocrit values. Hb analyses using the Hb Gold Analyzer showed Hb A₂ (72.5%) and Hb F (30.0%) without Hb A while the capillary electrophoresis revealed 2.3% Hb A₂ and a major peak of Hb F (91.2%). Further molecular investigation identified that he was in fact a compound heterozygote for Hb Tak and deletional (δβ)(0)-thalassemia. Hematological parameters of the patient were compared with those observed for a Thai boy who demonstrated features of erythrocytosis and microcytosis caused by homozygous Hb Tak with α(+)-thalassemia and with those of pure carriers of Hb Tak and (δβ)(0)-thalassemia in our series. This report confirms the importance of both Hb and molecular investigations for the assessment of genotype/phenotype correlation and the appropriate management of the patients.