Background and Aims: Drug-induced liver injury with autoimmune features (AI-DILI) mimics the clinical presentation, and laboratory and pathologic features of idiopathic autoimmune hepatitis (AIH). We aimed to identify histopathologic hallmarks to differentiate these entities. Methods: All liver biopsies archived for the past 10 years were reviewed retrospectively to identify cases of recently detected liver injury associated with predominantly lymphoplasmacytic interphase hepatitis, positive markers for liver autoimmunity, and negative tests for viral hepatitis. Twenty cases were divided into AIH (n = 12) or AI-DILI (n = 8) groups. Blind qualitative evaluation of necroinflammatory changes and liver fibrosis were performed according to the Scheuer scoring system. Cellular densities were determined using ImageJ (V1.51t, National Institutes of Health, Bethesda, MD, USA). Fibrosis was assessed on Masson trichrome-stained slides, and collagen deposition was estimated following a protocol of color deconvolution. Results: Necroinflammatory changes as well as densities (portal and lobular) of neutrophils and eosinophils, intracellular cholestasis, and regenerative changes did not differ between the two groups (P ≥ 0.05). Neutrophil densities but not eosinophils showed a positive correlation with the severity of hepatocellular damage (r = 0.6 and 0.58, vs. alanine aminotransferase, P < 0.05). Ceroid-laden macrophages but not histiocytic aggregates appeared to be more common in AI-DILI (P < 0.05). AIH patients presented more often with evidence of chronic damage, including higher scores of fibrosis and collagen deposition, in comparison to AI-DILI (P < 0.05). Conclusions: Although there is no histologic feature pathognomonic for AI-DILI or AIH, advanced stages of liver fibrosis can be used to support the diagnosis of AIH in some cases. Definitive diagnosis of AI-DILI requires follow-up and demonstration of complete remission after drug withdrawal with no need for immunosuppression.
Keywords: Autoimmune hepatitis; DILI; Digital pathology; Liver fibrosis.