Immunology Highlights of Four Major Idiosyncratic DILI Subtypes Verified by the RUCAM: A New Evidence-Based Classification

Conventionally, drug-induced liver injury (DILI) exists in two types: idiosyncratic and intrinsic. Both types are classified as non-immune disorders, thereby ignoring that some iDILI cases may have an immune or autoimmune background that requires a different therapeutic approach because steroids may be helpful. The purpose of this analysis was to analyze and classify the subtypes of iDILI which, indeed, show autoimmune or immune features among four cohorts, namely idiosyncratic DILI type 1: idiosyncratic drug-induced autoimmune hepatitis (DIAIH), to be differentiated from the classic drug-unrelated idiosyncratic autoimmune hepatitis (AIH); idiosyncratic DILI type 2: human leucocyte antigen-based idiosyncratic drug-induced autoimmune hepatitis; idiosyncratic DILI type 3: anti-cytochrome P450-based idiosyncratic drug-induced autoimmune hepatitis; and idiosyncratic DILI type 4: immune-based idiosyncratic drug-induced liver injury associated with Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). In conclusion, the traditional non-immune and non-autoimmune iDILI, as well as the four immune or autoimmune iDILI subtypes, are now well classified and clinically characterized by the broadly applied Roussel Uclaf Causality Assessment Method (RUCAM), facilitating additional immunology and therapy studies for the four subtypes, all of which could benefit from steroid treatment.