Recently, there are new techniques for genetics study. We aimed to identify the associated genetic change of the agranulocytosis side effect of antithyroid drugs. First, we will look at the classical human Leukocyte Antigen (HLA) loci, such as HLA-A, -B, -C, -DR, -DQ and -DP. If no significant change is found in the above genes, we will consider whole exon sequencing with next-generation sequencing, Statistic analysis will include appropriate linkage analysis, association study, variation data analysis, pathway analysis. If we can identify the genetic change and perform genetic examinations before prescription, we can avoid the happening of severe side effects.