TYPE Sicilian (deltabeta)°-Thal (see Fig. 14)
CAUSE A 13,377 bp deletion spanning from the delta-IVS-II to ~6 kb 3' to the termination codon of the beta gene. The breakpoints are close to the other (deltabeta)°-thal deletions of similar size: Laotian and Thai.
DETECTION Gene mapping using different probes and enzymes. The 5' and 3' breakpoints were determined by cloning and sequencing. The exact 5' breakpoint occurs within the delta-IVS-II, 188 bp from the beginning of the third exon. The 3' breakpoint is located at 5,710 bp 3' to the termination codon of the beta gene, thus mapping into the L1 repetitive sequence.
PHENOTYPE Homozygotes have a thalassemia intermedia with Hb levels of 10 g/dl; 100% Hb F, and 50% Ggamma in Hb F. Heterozygotes show characteristics of deltabeta-thal trait with mild anemia, typical thalassemic RBC morphology, hypochromia, basophilic stippling, increased Hb F (4.0-18.6%), low-normal Hb A2 (2.3%), and 25-56% Ggamma levels.
DISTRIBUTION Mediterranean countries: Sicily, Italy, former Yugoslavia, Hungary, Greece, Turkey, Israel, Egypt.
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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.