TYPE Yunnanese Ggamma(Agammadeltabeta)°-Thal (see Fig. 16)
CAUSE A large deletion that removes ~90 kb of DNA including the Agamma, delta, and beta genes. The 5' breakpoint of the deletion is located ~130 bp upstream from the Agamma gene, whereas the 3' breakpoint is located ~66 kb 5' to the beta gene.
DETECTION Gene mapping with different enzymes and probes.
PHENOTYPE Heterozygotes have hematological indices similar to that of beta-thal trait except for lower than normal Hb A2 levels: Hb 12-15.3 g/dl; RBC 4.5-5.9 x 1012/l; MCV 72-75 fl; MCH 25.9-26.7 pg; Hb A2 1.5-1.7%; Hb F 9.3-16.5%; F-cells 26-45%; Ggamma 72-90%. Homozygotes have a mild anemia (Hb 10.7 g/dl), hypochromia and microcytosis, no splenomegaly, and 100% Hb F. The fetal chains are of the Ggamma type, and the distribution of Hb F in the heterozygote was pancellular.
DISTRIBUTION This deletion was found in a 19-year-old male from the Yunnan Province of China. He was the offspring of a first-cousin marriage.
1. Zhang, J-W., Song, W-F., Zhao, Y-J., Wu, G-Y., Qiu, Z-M., Wang, F-N., Chen, S-S., and Stamatoyannopoulos, G.: Blood, 81:1624, 1993.

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.