IDENTIFICATION OF HB C[BETA-6(A3)GLU-]LYS] IN A THAI MALE

The propositus was a 29-year-old Thai male, whose electrophoretic patt ern showed Hb A (58%) plus an abnormal hemoglobin (42%) with mobility identical to Hb A2 and Hb E. Protein sequencer analysis and tryptic pe ptide mapping of the beta chain indicated that the abnormal hemoglobin was Hb C [beta6(A3)Glu-->Lys], rather than Hb E which is more commonl y found in South East Asia. This conclusion was confirmed by direct se quence analysis of the propositus' DNA, which showed AAG as well as GA G at codon 6 of the beta gene, in agreement with heterozygosity for Hb C and Hb A. Furthermore, the beta gene framework (Ava II -, Bam HI +) of the propositus suggested that the beta(C) gene may have arisen fro m an independent mutation. Since Hb C and Hb E have the same mutation (Glu --> Lys) in the beta chain, although at different positions, and behave similarly in electrophoresis, cases of Hb C and Hb E may someti mes have been mistakenly identified for each other, based on whichever variant is most prevalent in the particular population.