Patients with one or two copies of the HLA-B*15:02:01 allele may have an increased risk for severe cutaneous adverse reactions when receiving lamotrigine as compared to patients with no HLA-B*15:02:01 alleles or negative for the HLA-B*15:02:01 test. However, conflicting evidence has been reported. Other genetic and clinical factors may also influence risk of lamotrigine-induced adverse reactions.