In our cohort, we found a potentially pathogenic homozygous variant of TH in a patient with PD without symptoms of DRD, and we also provide suggestive evidence that loss-of-function variants in the TH gene might contribute to an increased risk for sEOPD, which help us fully understand the genetic risk for PD conferred by the TH gene. The gene discussed is TH; the disease is Parkinson disease.