Macro-AST in an asymptomatic young patient.

Elevated enzyme activities in plasma may sometimes be due to the presence of macroenzymes.1,2 Macroenzymes are high molecular mass complexes of plasma enzymes with immunoglobulins (IgG, IgA or IgM) or other plasma components with reduced plasma clearance and prolonged half life, resulting in elevated serum activities due to the “trapping” of the enzymes in serum.3 These results may thus be erroneously considered as pathologic. Macro-aspartate aminotransferase (macro-AST) has rarely been reported as a benign cause for increased plasma aspartate aminotransferase (ASAT) activities.4,5-8