Idiopathic biliary ductopenia in adults: a report of five cases. The clinical and pathological findings of five adult cases of idiopathic nonsyndromatic paucity of interlobular bile ducts are reported. Patients were 18-32 years old at the onset of the disease; four presented with pruritus and/or jaundice and one with bleeding of the esophageal varices. Two patients were siblings. Serum alkaline phosphatase counts ranged from 1 to 16 times the upper normal value, and total bilirubin counts ranged from 0.6 to 8.8 mg/dL (10 to 150 mumol/L). Initial liver biopsy showed portal and periportal fibrosis with cholangiolar proliferation and reduction in the number of interlobular bile ducts. Antimitochondrial antibodies were absent, and bile ducts were normal after opacification. The patients were observed for 3-11 years. Repeated liver biopsies in the five patients showed progression of the lesions, with development of biliary type cirrhosis in four. Two of the four patients with cirrhosis died of hepatic failure 3 and 11 years after onset of the disease. In the two other cases, liver transplantation was performed successfully. These cases suggest that chronic cholestasis with marked ductopenia resembling the nonsyndromatic paucity described in infancy and childhood may reveal itself at an adult age. This disorder, possibly familial, may rapidly progress to severe and even fatal liver disease and could be a new indication for liver transplantation. 