TYPE Belgian Ggamma(Agammadeltabeta)°-Thal (see Fig. 16)
CAUSE The deletion spans ~50 kb, removing the 3' end of the Agamma, psibeta, delta, and beta genes. The 3' breakpoint of this deletion coincides with the 3' breakpoints of three other deletions in the beta-globin gene cluster, namely HPFH-3, HPFH-4, and the German Ggamma(Agammadeltabeta)°-thal. The 5' end of the deletion is very close to the 5' breakpoint of the Indian, Black, and Chinese Ggamma(Agammadeltabeta)°-thal.
DETECTION Gene mapping with different enzymes and probes.
PHENOTYPE Subjects heterozygous for the Belgian Ggamma(Agammadeltabeta)°-thal show microcytosis, a low MCV (61-73 fl), a low MCH, an increased alpha/gamma+beta chain ratio (1.5-2.8), elevated Hb F (14-23%), and normal Hb A2. Hb F consists of Ggamma chains and is heterogeneously distributed in the red cells.
DISTRIBUTION Found in a large Belgian family; delta°-thal, hereditary spherocytosis, and adenosine deaminase deficiency were also present, segregating independently in the same family.
1. Losekoot, M., Fodde, R., Gerritsen, E.J.A., van de Kuit, I., Schreuder, A., Giordina, P.C., Vossen, J.M., and Bernini, L.F.: Blood, 77:861, 1991.

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.