Autoimmune Hepatitis

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease driven by loss of immune tolerance to hepatocyte antigens. It predominantly affects young-to-middle-aged women and presents with elevated transaminases, fatigue, and sometimes acute liver failure. USMLE Step 1 tests this concept primarily through serology — you need to know which antibodies map to which AIH type — and through recognizing that management is immunosuppressive, not antiviral. The biopsy finding of interface hepatitis (lymphocytic inflammation at the portal-parenchymal junction) is the classic histologic anchor.

The exam loves to flip the antibody associations. Type 1 is the common form: ANA and anti-smooth muscle antibody (ASMA). Type 2 is rarer, seen more in children, and defined by anti-LKM1 (anti-liver-kidney microsomal antibody type 1). Students consistently mix these up, especially when a vignette emphasizes the liver-kidney connection in the antibody name and they incorrectly link it to the more common adult-onset type. USMLE Step 1 will exploit that confusion directly.

The management angle is also tested by misdirection. Because AIH is a liver disease and viral hepatitis is common, students sometimes reach for antivirals. That's wrong — AIH is autoimmune, so the treatment is immunosuppression with prednisone ± azathioprine. Associated autoimmune conditions (thyroiditis, celiac disease, rheumatoid arthritis) can appear in the vignette as contextual clues that the liver disease has an autoimmune etiology. Recognizing those associations helps you pick AIH over viral or drug-induced hepatitis.