Effect of NUDT15 polymorphisms on early hematological safety of low‐dose azathioprine in Chinese patients with pemphigus vulgaris: A prospective cohort study

Azathioprine (AZA) is the preferred immunosuppressant for treating pemphigus vulgaris (PV), with discontinuation mainly attributed to hematological adverse events (AE). Reportedly, nucleoside diphosphate‐linked moiety X‐type motif 15 (NUDT15) polymorphisms have been strongly associated with thiopurine‐induced leukopenia. To investigate hematological AE of low‐dose AZA based on NUDT15 genotypes among patients with PV, a prospective cohort study was conducted in patients with PV, followed‐up for the first 8 weeks after AZA administration. All patients were divided into wild homozygous and heterozygous NUDT15 groups. Both groups initiated AZA at low dose (50 mg/day) and continued with different dose‐escalating approaches. Bone marrow suppression was considered the principal outcome. Overall, 62 patients with PV were enrolled (48 in the wild homozygous NUDT15 group vs. 14 in the heterozygous NUDT15 group). Except for median maintenance doses of AZA, no statistically significant differences were observed between the two groups in terms of age, sex, white blood cells, neutrophil count, platelet count, hemoglobin level, median final doses of corticosteroids (mg prednisone equivalent), pemphigus disease area index, and anti‐desmoglein 1/3 autoantibodies. In both groups, patients presented similar hematological AE and treatment responses after administration of different low‐dose AZA treatment strategies. Low‐dose AZA based on NUDT15 genotypes can reduce the risk of early hematological AE among patients with PV.