A new cause of increased serum aspartate aminotransferase activity

Two healthy young women had an unexplained persistent elevation of aspartate aminotransferase (ASAT) activity. In both cases electrophoresis of serum ASAT isoenzymes displayed an abnormally moving fraction that comprised the whole serum activity, while liver and muscle revealed the normal cytoplasmic and mitochondrial isoenzymes. In the first case serum ASAT was found to be bound by serum IgG, in the second case the binding protein remained unidentified.