-(alpha)20.5,.this.20.5.kb.deletion.invo.html


MUTATION		-(alpha)20.5; this 20.5 kb deletion involves the entire alpha2 and the 5' end of the alpha1 gene (see Fig. 24)

AMINO ACID REPLACEMENT		None
TYPE OF ALPHA-THAL		alpha-Thal-1 [- -/]
MECHANISM		The deletion involves both alpha-globin genes; thus, no alpha-mRNAs are formed
IDENTIFICATION		Gene mapping; PCR methodology
HEMATOLOGY IN HETEROZYGOTE(S)		Hb 11-14 g/dl; MCV 65-72 fl; MCH 20-25 pg; Hb A₂ 2.0-2.5%; alpha/beta ratio 0.7-0.8
HEMATOLOGY IN HOMOZYGOTE(S)		Hydrops fetalis
OCCURRENCE		In various Mediterranean and Central Asian populations
HAPLOTYPE		Not determined
FOUND IN COMBINATION WITH ABNORMAL HB(S)		Not reported
FOUND IN COMBINATION WITH alpha-THAL ALLELE(S)		Mainly the -alpha(3.7 kb) deletion; the 5 nt nondeletional alpha-thal-2, etc. causing Hb H disease: Hb 9.5-12.5 g/dl; MCV 63-77 fl; MCH 17-24 pg; Hb A₂ 0.6-1.0%; Hb H 10-20%; alpha/beta ratio 0.4-0.5
OTHER INFORMATION		None


REFERENCES
1.		Nicholls, R.D., Higgs, D.R., Clegg, J.B., and Weatherall, D.J.: Blood, 65:1434, 1985.
2.		Bowden, D.K., Vickers, M.A., and Higgs, D.R.: Br. J. Haematol., 81:104, 1992.

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.