Hb H disease resulting from the association of an alpha(0)-thalassemia allele [-(alpha)(20.5)] with an unstable alpha-globin variant [Hb Icaria]: First report on the occurrence in Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Hb H Disease is caused by the loss or inactivation of three of the four functional alpha-globin genes. Patients present chronic hemolytic anemia and splenomegaly. In some cases, occasional blood transfusions are required. Deletions are the main cause of this type of thalassemia (alpha-thalassemia). We describe here an unusual case of Hb H disease caused by the combination of a common alpha(0) deletion [-(alpha)(20.5)] with a rare point mutation (c.427T > A), thus resulting in an elongated and unstable alpha-globin variant, Hb Icaria, (X142K), with 31 additional amino-acid residues. Very high levels of Hb H and Hb Bart's were detected in the patient's red blood cells (14.7 and 19.0%, respectively). This is the first description of this infrequent association in the Brazilian population.324712715Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [02/13801-7