The role of histologic evaluation in the diagnosis and management of autoimmune hepatitis and its variants.
The diagnosis of autoimmune hepatitis requires a constellation of clinical, laboratory, and histologic features that exclude other conditions and support the syndrome. Interface hepatitis is the histologic hallmark of the disease, and it may be associated with panacinar hepatitis with or without bridging necrosis or multiacinar necrosis. The liver tissue examination at accession supports the diagnosis and assesses disease severity. It can also suggest the diagnosis in patients with atypical presentations, including those with an acute onset or cryptogenic disease. The liver tissue examination during therapy defines end points of treatment (remission) and evaluates unexpected outcomes (treatment failure, incomplete response). Manifestations of bile duct injury are incompatible with the classic diagnosis of autoimmune hepatitis, and they may be coincidental findings of no or uncertain clinical significance or weak expressions of a variant form. Histologic features of autoimmune hepatitis may intermix with those of PBC, PSC, and chronic hepatitis C infection, or they may occur in autoimmune cholangitis or cryptogenic chronic hepatitis. Conditions in which the histologic findings suggest the overlap of two disorders or are insufficient for designation as classic disease constitute the variant syndromes.