TYPE Black Ggamma(Agammadeltabeta)°-Thal (see Fig. 16)
CAUSE A 35.7 kb deletion starting in the IVS-II in the Agamma gene to 200 bp from the 3' end of the L1 repetitive sequence. The deletion removes the 3' end of the Agamma, psibeta, delta, and beta genes.
DETECTION Gene mapping with different enzymes and probes; cloning and sequencing. The 5' end is 87 bp from the 5' end of exon 3 of the Agamma gene. Eleven bases occurring at the deletion junction do not appear to be derived from either the 5' or the 3' normal sequences. This deletion is very similar to the Turkish Ggamma(Agammadeltabeta)°-thal, both in size and location of the breakpoints.
PHENOTYPE Heterozygotes exhibit typical thalassemic features with a mild anemia, microcytosis, and hypochromia. Compound heterozygotes with Hb S have mild anemia, variable microcytosis, normal Hb A2 (2.3%) but elevated Hb F levels (19.2%). The following table lists hematological data for several subjects with a simple heterozygosity (AF) and compound heterozygosity (SF).
DISTRIBUTION Found in several Black families in the Southeastern United States.
1. Henthorn, P.S., Smithies, O., Nakatsuji, T., Felice, A.E., Gardiner, M.B., Reese, A.L., and Huisman, T.H.J.: Br. J. Haematol., 59:343, 1985.
2. Henthorn, P.S., Smithies, O., and Mager, D.L.: Genomics, 6:226, 1990.

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.