A 75‐year‐old male with prostate cancer and multiple bone metastases developed grade 2 rash and grade 3 liver dysfunction according to the Common Terminology Criteria for Adverse Events (CTCAE) 3 weeks after starting apalutamide with a GnRH antagonist, followed by a 3‐day fever. The gene discussed is GNRH1; the disease is Skin rash.