TYPE Chinese Ggamma(Agammadeltabeta)°-Thal (see Fig. 16)
CAUSE A large deletion of ~100 kb that starts within the Agamma-IVS-II and extends ~75 kb downstream from the beta gene. The Chinese (Agammadeltabeta)°-thal differs in size from the HPFH-1 and HPFH-2 by less than 10 kb. The 5' breakpoint of the Chinese deletion is 6 kb upstream of the 5' breakpoint of HPFH-2, and the 3' breakpoints of the two deletions are 11 kb apart. Therefore, the Chinese (Agammadeltabeta)°-thal deletion is 5 kb shorter than the HPFH-2 deletion.
DETECTION Gene mapping with different probes and enzymes. The exact breakpoints of this large deletion were characterized by cloning and sequencing.
PHENOTYPE Heterozygotes show a mild hypochromia and microcytosis with 2.7% Hb A2 and 11.8% Hb F (range 9.3-15.7%). The Ggamma in Hb F was not reported and the alpha/non-alpha ratio was 1.3. Two families were studied; one individual was a compound heterozygote for the deletion and beta°-thal. The Hb F consisted of Ggamma chains only.
DISTRIBUTION This condition was reported in two unrelated familes from Southern China.
1. Jones, R.W., Old, J.M., Trent, R.J., Clegg, J.B., and Weatherall, D.J.: Nucleic Acids Res., 9:6813, 1981.
2. Mager, D.L., Henthorn, P.S., and Smithies, O.: Nucleic Acids Res., 13:6559, 1985.

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.