Abstract: Wang Lian, Zhou Yanhong, Zhou Xingli, Lyu Xiaoyan, Zeng Xin, Li Wei Department of Dermatology, West China Hospital, Sichuan University, Chengdu 610041, China （Wang L, Zhou XL, Lyu XY, Li W）; Department of Laboratory Medicine, West China Hospital, Sichuan University, Chengdu 610041, China（Zhou YH）; Department of Oral Mucosal Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu 610041, China （Zeng X） Corresponding author: Li Wei, Email: liwei@mcwcums.com 【Abstract】 A 49-year-old male patient presented with repeated oral erosions for 1 year, as well as cutaneous erythema and blisters for 1 month. According to histopathological examination and detection of specific antibodies of pemphigus, the patient was diagnosed with pemphigus vulgaris. After the treatment with oral prednisone and azathioprine for 1 month, the white blood cell count and segmented neutrophilic granulocyte count both decreased. After withdrawal of azathioprine, the patient was subcutaneously injected with 150 μg recombinant human granulocyte colony-stimulating factor for 1 session. Then, the white blood cell count became normal. Genotyping test revealed that the patient carried a heterozygous mutation in the NUDT15 gene（JZ274）, and was homozygous for wild-type TPMT*2, TPMT*3C and ITPA genes. The patient was diagnosed with azathioprine-induced myelosuppression.