MUTATION TAA->AAA at codon 142 of the alpha2 gene
AMINO ACID REPLACEMENT Stop codon->Lys + 30 additional amino acids (Hb Icaria)
TYPE OF ALPHA-THAL alpha-Thal-2 [alpha(T)alpha/alphaalpha]
MECHANISM The T->A mutation results in extension of the alpha chain at the C-terminus with 31 amino acid residues; a stop codon is found at the new codon 173
IDENTIFICATION By protein analysis; amplification of the alpha2-globin gene and sequencing; dot-blot analysis with allele specific probes; ASO
HEMATOLOGY IN HETEROZYGOTE(S) Hb 11.5-12.5 g/dl; MCV 78-86 fl; MCH 25-28 pg; Hb A2 2.3-2.7%
OCCURRENCE In the populations of Greece and the Balkan countries
HAPLOTYPE Not determined
FOUND IN COMBINATION With various alpha-thal-2 and alpha-thal-1 alleles resulting in Hb H disease (see Refs. 3 and 4)
OTHER INFORMATION Hb Icaria is present for <0.5% in heterozygotes; the variant is unstable
1. Clegg, J.B., Weatehrall, D.J., Contopolou-Griva, I., Caroutsos, K., Poungouras, P., and Tsevrenis, H.: Nature, 251:245, 1974.
2. Efremov, G.D., Josifovska, O., Nikolov, N., Codrington, J.F., Oner, C., Gonzalez-Redondo, J.M., and Huisman, T.H.J.: Br. J. Haematol., 75:250, 1990.
3. Traeger-Synodinos, J., Kanavakis, E., Tzetis, M., Kattamis, A., and Kattamis, C.: Am. J. Hematol., 44: 162, 1993.
4. Kanavakis, E., Traeger-Synodinos, J., Papasotiriou, I., Vrettou, C., Metaxotou-Mavromati, A., Stamoulakatou, A., Lagona, E., and Kattamis, C.: Br. J. Haematol., 92:332, 1996.

This material is from the book A Syllabus of Thalassemia Mutations (1997) by Titus H.J. Huisman, Marianne F.H. Carver, and Erol Baysal, published by The Sickle Cell Anemia Foundation in Augusta, GA, USA. Copyright © 1997 by Titus H.J. Huisman. All rights reserved. Neither this work nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, microfilming and recording, or by any information storage and retrieval systems, without permission in writing from the Author.