PDCD1 and Erythema: In our case, the patient exhibited erythema and blister formation approximately 15 months after initiating karelizumab therapy, and these were most prevalent on the chest, back, and scalp—areas abundant in hair follicles—suggesting that the inflammation induced by the PD-1/PD-L1 inhibitor may have led to the exposure of hair follicle antigens, resulting in a loss of immune privilege (13).