Histology may be able to distinguish between CTLA-4 inhibitor-induced hepatitis, in which there is often the presence of fibrin ring granulomas and central vein endotheliitis, and that related to PD-1 and PD-L1 inhibitor-induced hepatitis, in which more extensive lobular hepatitis is generally apparent [8, 11, 51]. The gene discussed is PDCD1; the disease is hepatitis A virus infection.