Clinicopathological study of primary biliary cirrhosis negative for antimitochondrial antibodies

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Abstract
Primary biliary cirrhosis (PBC) is characterized by the occurrence of antimitochondrial antibodies (AMA) and the progressive destruction of intrahepatic bile ducts, followed by biliary cirrhosis. However, there are about 5% of PBC patients who show clinicopathological features of PBC but are negative for AMA. In this study, clinicopathological features, as well as antibody reactivity against recombinant (r)‐mitochondrial polypeptides, were examined in 30 AMA negative PBC patients and 38 AMA positive PBC patients, in whom the presence of AMA had been determined by indirect immunofluorescence (IF). There were few differences in the clinical and serological features between both groups. Histopathologic features, including staging, bile duct lesions and granuloma, were also similar in both groups. Among the 30 IF‐tested AMA negative patients, 29 were also negative against beef heart mitochondrial proteins, but 24 reacted to one or more of the following r‐polypeptides, as determined by immunoblotting: E1 alpha of pyruvate dehydrogenase complex, the E2 subunit of pyruvate dehydrogenase complex, and the branched‐chain 2‐oxo‐acid dehydrogenase complex. The remaining six AMA‐negative patients were asymptomatic, and histologically resembled having stage 1 of the disease, with relatively mild lymphocytic piecemeal necrosis. One case was positive for anti‐smooth muscle antibody. The other clinicopathological features of these patients were similar to those of other AMA negative patients. The present study found that a majority of the AMA‐negative patients fulfilling other clinicopathological criteria of PBC, had features similar to the AMA‐positive PBC patients, and that a majority of IF AMA‐negative patients were positive for r‐polypeptides of the 2‐oxo‐acid dehydrogenase complex. It seems that nearly all the AMA negative patients possess a broad spectrum of antibody profile of AMA, in addition to clinicopathological and serological features.