Clinical Characteristics of Genuine Acute Autoimmune Hepatitis

<b><i>Introduction:</i></b> Autoimmune hepatitis (AIH) has a spectrum of symptoms ranging from asymptomatic disease to acute severe hepatitis, chronic hepatitis, and decompensated cirrhosis. The acute presentation is not rare and could represent genuine acute AIH (GAAIH) or acute exacerbation of chronic autoimmune hepatitis. We aimed to identify the prevalence, clinical features, and prognostic factors associated with GAAIH and compare these cases with acute exacerbation of chronic AIH. <b><i>Methods:</i></b> This cross-sectional observational study evaluated patients with acute AIH presentation, defined as total bilirubin &gt;5 times the upper limit of normality (xULN) and/or alanine aminotransferase &gt;10 xULN, and no prior history of liver disease. Histology findings of acute disease defined GAAIH. Bivariate analyses were performed to identify factors associated with the GAAIH, when compared with acute exacerbation of chronic AIH. <b><i>Results:</i></b> Seventy-two patients with acute presentation of AIH were included and six (8.3%) of them presented GAAIH. Comparative analysis between patients with GAAIH and patients with acute exacerbation of chronic AIH revealed that prothrombin activity (96% [74–100] vs. 61% [10–100]; <i>p</i> = 0.003) and albumin levels (3.9 ± 0.2 g/dL vs. 3.4 ± 0.5 g/dL; <i>p</i> &lt; 0.001) were higher in patients with GAAIH. The International Autoimmune Hepatitis Group score was higher in patients with acute exacerbation of chronic AIH (18.5 [8–23] vs. 16.5 [15–17]; <i>p</i> = 0.010). Compared to 15.2% of acute exacerbation of chronic AIH, complete therapeutic response to treatment was achieved in 67.7% of cases with GAAIH (<i>p</i> = 0.018). <b><i>Conclusions:</i></b> GAAIH was rare (8.3%), and patients with this presentation exhibited more preserved liver function tests, suggesting that most cases presenting with loss of function are acute exacerbation of chronic AIH. Additionally, patients with GAAIH had a better complete therapeutic response, suggesting a more preserved liver function at presentation, and early diagnosis has a positive therapeutic implication.