TUESDAY, Nov. 4, 2025 (HealthDay News) -- Two human leukocyte antigen (HLA) class I alleles are independently associated with an increased risk for allopurinol-induced severe cutaneous adverse reactions (SCARs), according to a study published online Oct. 29 in JAMA Dermatology.

Chelsea N. Campbell, from Vanderbilt University Medical Center in Nashville, Tennessee, and colleagues examined the association of HLA class I and II among U.S. patients who received a diagnosis of allopurinol-induced Stevens-Johnson syndrome and toxic epidermal necrolysis or drug reaction with eosinophilia and systemic symptoms compared to allopurinol-tolerant and population control participants. Participants were identified from the Vanderbilt University Medical Center biobank, which includes 94,489 individuals with imputed HLA class I and II typing.

The genetic association study included 16 patients with allopurinol-induced SCAR and 160 allopurinol-tolerant control participants. The researchers found independent associations for two HLA class I alleles with an increased risk for allopurinol-induced SCAR: HLA-B*58:01 and HLA-A*34:02 (odds ratios, 28.0 and 20.6, respectively). There were no HLA class II alleles that met the Bonferroni-corrected P < 0.05 level of significance.

"We found a new genetic association, HLA-A*34:02, which appears very important as a risk factor in U.S. allopurinol severe cutaneous adverse reactions patients," coauthor Elizabeth J. Phillips, M.D., also from Vanderbilt University Medical Center, said in a statement. "The combination of HLA-A*34:02 and HLA-B*58:01 would help explain risk in over 80 percent of patients."

One author disclosed ties to the pharmaceutical and medical technology industries.

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