Yang first identified the role of NUDT15-rs116855232 in Korean subjects with Crohn's disease treated with thiopurines in 2014[11]; in this paper, we present a case of a Crohn's disease (CD) patient receiving oral AZA with mutant (CT allele) NUDT15-rs116855232 and normal TPMP activity, who developed severe pneumonia caused by toxoplasma gondii infection. The gene discussed is NUDT15; the disease is Crohn disease.