Isolated aspartate aminotransferase elevation due to macroenzyme formation with liver biopsy correlation.

Serum aspartate aminotransferase (AST) has rarely been reported to complex with immunoglobulins, resulting in abnormally elevated serum activity. A similar phenomenon occurs with serum amylase, resulting in the more common entity of macroamylasemia. AST macroenzyme formation can occur in the presence or absence of liver disease and, at times, can lead to a false suspicion of liver disease. We describe the abnormal liver histology found in a healthy patient with isolated AST elevation due to AST macroenzyme formation.