Simple PCR detection of haptoglobin gene deletion in anhaptoglobinemic patients with antihaptoglobin antibody that causes anaphylactic transfusion reactions

Two anhaptaglobinemic patients showing anaphylactic transfusion reactions b y antihaptoglobin antibody were found. Southern blot analysis indicated tha t 2 patients were homozygous for the deleted allele of the haptoglobin gene (Hp(del)) as reported previously. We have identified the junction region o f the deletion from genomic DNA of 1 patient using cassette-mediated polyme rase chain reaction (PCR). Then, the deleted region from the 5' breakpoint to the promoter region of the Hp was amplified from genomic DNA of a contro l individual using PCR. DNA sequence analysis of these regions indicated th at the 5' breakpoint of the Hp(del) allele was located 5.2 kilobase (kb) up stream of exon 1 of the Hp and the 3' breakpoint was positioned between 52 and 53 base pair (bp) upstream of exon 5 of the haptoglobin-related gene. T here was no significant homology between the DNA sequences flanking the 5' and 3' breakpoints, except for a 2-bp (TG) identity. To examine the gene fr equency, we have developed a simple PCR method to detect the gene deletion. We found 8, 16, and 17 Hp(del), alleles in 157 Koreans, 523 Japanese, and in 284 Chinese, respectively, but did not find the Hp(del) in 101 Africans or In 100 European-Africans. The incidence of individuals homozygous for th e Hp(del) allele was therefore expected to be 1/4000 in Japanese,1/1500 in Koreans, and 1/1000 in Chinese. This incidence is higher than that of IgA d eficiency in Japanese. More attention should be paid on haptoglobin deficie ncy and antihaptoglobin antibody as the cause of transfusion-related anaphy lactic reactions in Asian populations.