Hb H Disease is caused by the loss or inactivation of three of the four functional α-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 (α-thalassemia). We describe here an unusual case of Hb H disease caused by the combination of a common α0 deletion [-(α)20.5] with a rare point mutation (c.427T > A), thus resulting in an elongated and unstable α-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. Copyright © 2009, Sociedade Brasileira de Genética.324712715Clegg, J.B., Weatherall, D.J., Contopolou-Griva, I., Caroutsos, K., Poungouras, P., Tsevrenis, H., Haemoglobin Icaria, a new chain-termination mutant which causes alpha thalassaemia (1974) Nature, 251, pp. 245-247Dacie, J.V., Lewis, S.M., Bain, B.J., Bates, I., (2006) Practical Haematology, , 9th edition. Artmed, Porto Alegre, 572 ppDodé, C., Rochette, J., Krishnamoorthy, R., Locus assignment of human alpha globin mutations by selective amplification and direct sequencing (1990) Br J Haematol, 76, pp. 275-281Efremov, G.D., Josifovska, O., Nikolov, N., Codrington, J.F., Oner, C., Gonzalez-Redondo, J.M., Huisman, T.H., Hb Icaria-Hb H disease: Identification of the Hb Icaria mutation through analysis of amplified DNA (1990) Br J Haematol, 75, pp. 250-253Hardison, R.C., Chui, D.H.K., Giardine, B., Riemer, C., Patrinos, G.P., Anagnou, N., MillerWand Wajcman, H., Hb Var: A relational database of human hemoglobin variants and thalassemia mutations at the globin gene server (2002) Hum Mut, 19, pp. 225-233Higgs, D.R., Weatherall, D.J., The alpha thalassaemias (2009) Cell Mol Life Sci, 66, pp. 1154-1162Kanavakis, E., Traeger-Synodinos, J., Papasotiriou, I., Vrettou, C., Metaxotou-Mavromati, A., Stamoulakatou, A., Lagona, E., Kattamis, C., The interaction of alpha zero thalassaemia with Hb Icaria: Three unusual cases of haemoglobinopathy H (1996) Br J Haematol, 92, pp. 332-335Kattamis, A.C., Camaschella, C., Sivera, P., Surrey, S., Fortina, P., Human alpha-thalassemia syndromes: Detection of molecular defects (1996) Am J Hematol, 53, pp. 81-91Schrier, S.L., Bunyaratvej, A., Khuhapinant, A., Fucharoen, S., Aljurf, M., Snyder, L.M., Keifer, C.R., Mohandas, N., The unusual pathobiology of hemoglobin constant spring red blood cells (1997) Blood, 89, pp. 1762-1769Steinberg, M.H., Forget, B.G., Higgs, D.R., Nagel, R.L., (2001) Disorders of Hemoglobin - Genetics, Pathophysiology and Clinical Management, , Cambridge University Press, New York, 1268 ppTan, A.S., Quah, T.C., Low, P.S., Chong, S.S., A rapid and reliable 7-deletion multiplex polymerase chain reaction assay for alpha-thalassemia (2001) Blood, 98, pp. 250-251Turbpaiboon, C., Limjindaporn, T., Wongwiwat, W., U-Pratya, Y., Siritanaratkul, N., Yenchitsomanus, P.T., Jitrapakdee, S., Wilairat, P., Impaired interaction of alpha-haemoglobin-stabilising protein with alpha-globin termination mutant in a yeast two-hybrid system (2006) Br J Haematol, 132, pp. 370-373Waggoner, S.A., Liebhaber, S.A., Regulation of alphaglobin mRNA stability (2003) Exp Biol Med, 228, pp. 387-395Wajcman, H., Traeger-Synodinos, J., Papassotiriou, I., Giordano, P.C., Harteveld, C.L., Baudin-Creuza, V., Old, J., Unstable and thalassemic alpha chain hemoglobin variants: A cause of Hb H disease and thalassemia intermedia (2008) Hemoglobin, 32, pp. 327-349Weatherall, D.J., Clegg, J.B., (2001) The Thalassaemia Syndromes, , 4th edition. Blackwell Science, Oxford, 864 pp