Complete remission of refractory pemphigus vulgaris in a Chinese patient with mutated NUDT15 by combination of minimal doses of azathioprine and prednisone.

Although azathioprine (AZA) combined with corticosteroids remains the first-line therapy to treat patients with pemphigus vulgaris (PV), there are increasing reports of AZA-induced leukopenia, which provides the rationale for monitoring the blood cell count and testing the genotypes at the thiopurine methyltransferase (TPMT) and the nucleoside diphosphate-linked moiety X-type motif 15 (NUDT15) genes. Here, we reported a case of persistent refractory PV in a Chinese patient with three runs of AZA-corticosteroids treatment. In the first two runs he received AZA-corticosteroids at standard or slightly reduced doses and developed leukopenia. In the third run of treatment, he was found to have NUDT15 mutation (rs116855232) and wild-type homozygous TPMT*3C (rs1142345), treatment with minimal doses of AZA and prednisone resulted in a complete remission of PV without any side effects including leukopenia. Our observations not only highlight the benefits of testing the TPMT and NUDT15 genotypes and monitoring the dynamic changes of the white blood cell count in guiding the AZA therapy, but also suggest the potential of using the AZA-corticosteroids combination at very low doses in the treatment of refractory PV.