Fulminant hepatic failure in northern Brazil: morphological, immunohistochemical and pathogenic aspects of Lábrea hepatitis and yellow fever.

A morphological evaluation of histopathological liver samples from 42 fulminant hepatic failure cases from the Amazon Basin was undertaken in order to differentiate yellow fever (YF) from Lábrea hepatitis (LH) and other entities. The pattern and distribution of liver cell death as well as ballooning degeneration and midzonal apoptotic bodies were the most distinctive features of YF, whereas morula cells were the major finding for LH. Nineteen well characterised cases were further submitted to immunohistochemical studies for expression of YF antigen, hepatitis B surface antigen (HBsAg) and delta virus antigen. In both diseases, but particularly in LH, portal vein branch phlebitis was evident and might have played a role in the pathogenesis of hepatic injury, leading to hepatic extinction and portal tract approximation. The regeneration pattern was remarkable: a high proliferative index was detected in YF, whereas in LH multinucleation and pseudoacinar transformation, associated with portal type I collagen deposition and portal elastic fibre proliferation, was seen. In conclusion, midzonal apoptosis, portal phlebitis and a high proliferative index in patients without evidence of previous liver injury was the dominant picture in YF. On the other hand, LH cases showed extensive, predominantly lytic hepatocytic necrosis, portal and hepatic vein phlebitis and morula cells in patients with a morphological background of chronic liver disease.