BACKGROUND: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe cutaneous adverse drug reactions. Human leukocyte antigens (HLA) may play an important role in the pathogenesis of SJS/TEN. AIMS: This study aims to identify HLA-B alleles in Vietnamese patients with SJS/TEN and to investigate the possible link between HLA-B alleles and causative drugs. MATERIALS AND METHODS: Sixty patients including SJS (30 patients) and TEN (30 patients) were enrolled in a cross-sectional descriptive study at two hospitals in Hanoi, Vietnam, from July 2018 to July 2019. Clinical features and laboratory findings were noted, HLA-B alleles were analyzed by the polymerase chain reaction (PCR)-sequence-specific oligonucleotide assay and LuminexTM Multiplex Technology. RESULTS: The most common HLA-B allele was HLA-B*15:02 (41.7%) followed by HLA-B*58:01 (25%) and HLA-B*46:01 (15%). Of the 25 patients possessing HLA-B*15:02 allele, culprit medicines were carbamazepine (13 patients; 52%), traditional medicine (two patients; 8%), and unknown drugs (seven patients; 28%). Of the 15 patients carrying HLA-B*58:01 allele, there were 13 patients whose offending medicine was allopurinol. Of the eight patients whose culprit drug was traditional medicine, there were 6 patients (75%) carrying HLA-B*51:02. Patients who carry HLA-B*15:02 were found to have 4 times higher risk of developing carbamazepine-induced SJS/TEN as compared with the tolerant control group (OR=4.17; 95% CI=2.07–8.37; p < 0.001). CONCLUSION: HLA-B*15:02 was the most common HLA-B allele in Vietnamese patients with SJS/TEN. In traditional medicine-induced SJS/TEN patients, HLA-B*51:02 allele might play an important role. The link between the HLA-B genotypes and causative drugs may suggest physicians to avoid risk medications for certain patients.

The frequencies and diversities of human leukocyte antigen (HLA) alleles and haplotypes are representative of ethnicities. Matching HLA alleles is essential for many clinical applications, including blood transfusion, stem cell transplantation, and tissue/organ transplantation. To date, the information about the frequencies and distributions of HLA alleles and haplotypes among the Kinh Vietnamese population is limited because of the small sample size. In this study, more than 3,750 cord blood units from individuals belonging to the Kinh Vietnamese population were genotyped using PCR sequence-specific oligonucleotide (PCR-SSO) for HLA testing. The results of the study demonstrated that the most frequently occurring HLA-A, -B, -C, and -DRB1 alleles were A*11:01 (25%), A*24:02 (12.3%), A*02:01 (11.2); A*03:03 (8.95%), A*02:03 (7.81%), A*29:01 (7.03%); B*15:02 (15.1%), B*46:01 (10.7%), B*58:01 (7.65%), B*38:02 (7.29%); C*08:01 (17.2), C*07:02 (16.2%), C*01:02 (15.2), C*03:02 (8.3%), C*15:05 (6.13); DRB1*12:02 (31.0%), DRB1*09:01 (10.47%), DRB1*15:02 (7.54%); DRB1*07:01 (6.68%), DRB1*10:01 (6.63%), respectively, with the highest allele diversity level observed in locus B (93 alleles). The most frequent haplotypes of two-locus combinations of HLA-A–B, HLA-A–C, HLA-A–DRB1, HLA-B–C, HLA-B–DRB1, and HLA-C–DRB1 haplotypes were A*11:01–B*15:02 (7.63%), A*11:01–C*08:01 (7.98%), A*11:01–DRB1*12:02 (10.56%), B*15:02–C*08:01 (14.0%), B*15:02–DRB1*12:02 (10.47%), and C*08:01–DRB1*12:02 (11.38%), respectively. In addition, the most frequent haplotypes of three- and four-locus sets of HLA-A–B–C, HLA-A–B–DRB1, HLA-A–C–DRB1, HLA-B–C–DRB1, and HLA-A–B–C–DRB1 were A*11:01–B*15:02–C*08:01 (7.57%), A*11:01–B*15:02–DRB1*12:02 (5.39%), A*11:01–C*08:01–DRB1*12:02 (5.54%), B*15:02–C*08:01–DRB1*12:02 (10.21%), and A*11:01–B*15:02–C*08:01–DRB1*12:02 (5.45%), respectively. This study provides critical information on the frequencies and distributions of HLA alleles and haplotypes in the Kinh Vietnamese population, accounting for more than 85% of Vietnamese citizens. It paves the way to establish an umbilical cord blood bank for cord blood transplantation programs in Vietnam.

Allopurinol (ALP) is commonly used as a drug for gout treatment. However, ALP is known to cause cutaneous adverse reactions (CARs) in patients. The HLA-B*58:01 allele is considered a biomarker of severe CAR (SCAR) in patients with gout, with symptoms of Stevens Johnson syndrome, and with toxic epidermal necrolysis. However, in patients with gout and mild cutaneous adverse drug reactions (MCARs), the role of HLA-allele polymorphisms has not been thoroughly investigated. In this study, 50 samples from ALP-tolerant patients and ALP-induced MCARs patients were genotyped in order to examine the polymorphisms of their HLA-A and HLA-B alleles. Our results showed that the frequencies of HLA-A*02:01/HLA-A*24:02 and HLA-A*02:01/HLA-A*29:01, the dual haplotypes in HLA-A, in patients with ALP-induced MCARs were relatively high, at 33.3% (7/21), which was HLA-B*58:01-independent, while the frequency of these dual haplotypes in the HLA-A locus in ALP-tolerant patients was only 3.45% (1/29). The HLA-B*58:01 allele was detected in 38% (8/21) of patients with ALP-induced MCARs, and in 3.45% (1/29) of ALP-tolerant patients. Notably, although HLA-B*58:01 may be a cause for the occurrence of MCARs in patients with gout, this correlation was not as strong as that previously reported in patients with SCAR. In conclusion, in addition to the HLA-B*58:01 allele, the presence of the dual haplotypes of HLA-A*02:01/HLA-A*24:02 and/or HLA-A*02:01/HLA-A*29:01 in the HLA-A locus may also play an important role in the appearance of ALP-induced MCARs in the Vietnamese population. The obtained primary data may contribute to the development of suitable treatments for patients with gout not only in Vietnam but also in other Asian countries.

Human leucocyte antigen (HLA) alleles are very diverse and characterized by ethnicity. To date, information about the frequencies and distributions of HLA alleles among the Vietnamese population is still limited. In this study, HLA‐DQB1 alleles of 2076 cord blood units from individuals belonging to Vietnam's Kinh ethnic people were genotyped using Luminex‐based polymerase chain reaction sequence‐specific oligonucleotide. The results of the study demonstrated that there were 23 alleles on the locus HLA‐DQB1. Among those, there were six alleles with high frequencies of over 5%, including DQB1*03:01 (35.9%), DQB1*05:01 (12.8%), DQB1*03:03 (12.2%); DQB1*06:01 (7.20%), DQB1*05:02 (6.62%) and DQB1*02:01 (5.30%) and five rare alleles with low frequencies of below 0.1%. More importantly, this study for the first time reported the presence of two new rare alleles including DQB1*01:01 and DQB1*01:02. Conclusively, this study provided significant information about HLA‐DQB1 alleles for further investigations and clinical applications.