A large beta-thalassemia deletion in a family of Indonesian-Malay descent.

The partial molecular characterization of a large deletion present in two members of an Indonesian-Malay family with beta-thalassemia trait is described. Polymerase chain reaction and sequencing analyses of the breakpoint identified a sequence which has previously been described in patients with the 45 kb Filipino beta 0-thalassemia deletion, i.e. a 5' breakpoint at position -4279 nucleotides 5' from the Cap site of the beta-globin gene. The 3' breakpoint is located in an L1 family of repetitive sequences at an unknown distance from the beta-globin gene. The hematological and hemoglobin data of the patients with this beta 0-thalassemia deletion further supports the concept that the unusually high Hb A2 levels are unique to deletions removing the 5' beta-globin gene region, and points to the importance of the 3' junction sequences for the regulation of Hb F levels in patients with deletional defects of the beta-globin gene cluster.