Histopathology of de novo autoimmune hepatitis.

De novo autoimmune hepatitis (DAIH) is a well-recognized complication of pediatric liver transplantation (LT). The diagnosis is largely based on elevated liver function test results and the development of autoimmune antibodies. The histology of DAIH was first described in 1998. We present detailed histological data from the largest series to date of pretreatment and posttreatment biopsy samples from pediatric LT patients with DAIH. The histological evaluation included first an assessment of the predominant pattern of injury (hepatitis, rejection, or bile duct obstruction). Then, the necroinflammatory activity (interface, lobular, and perivenular), plasma cell density, rejection activity index, and fibrosis were scored. Seventy of 685 pediatric patients (10.2%) who underwent LT developed DAIH according to clinical and biopsy findings. Fifty-one pretreatment biopsy samples and 38 posttreatment biopsy samples were available for a retrospective review. The predominant pattern of injury (hepatitis, rejection, or bile duct obstruction) was determined, and biopsy samples were scored for the necroinflammatory activity (interface, lobular, and perivenular), plasma cell density, rejection activity index, and fibrosis. The most common pattern of injury was lobular hepatitis, which was frequently unaccompanied by interface necroinflammatory activity or prominent plasma cell infiltrates. Seven of the 51 cases had features strongly suggestive of acute rejection. Posttreatment biopsy samples showed a reduction in the degree of necroinflammatory activity and plasma cell infiltrates. In most patients, the degree of fibrosis was stable or had regressed. Because the histological features of DAIH are variable and nonspecific, a high index of suspicion and correlation with autoimmune antibodies are necessary to establish the diagnosis. In the majority of patients with DAIH, treatment appears to yield good clinical outcomes and histological improvements.