Introduction: Macroenzymes are high molecular weight complex formed by the binding of one enzyme and a serum macromolecule, responsible for an increase in the activity of the corresponding enzyme in blood assay.
Case reports: We report two cases: firstly, a macro-aspartate aminotransferase (macro-ASAT) discovered in an 82-year-old woman who presented with an isolated and persistent elevation of the ASAT activity that was discovered after sepsis, secondly, a macro-creatine-kinase (macro-CPK) diagnosed in a 62-year-old man after several years of investigations for a persistent CPK elevation. These two case reports allowed us to discuss the mechanism leading to the formation of macroenzymes and the usefulness of their determination. Although macroenzymes are generally non pathologic, they may be associated with auto-immune, neoplastic or infectious diseases.
Conclusion: The possibility of a macroenzyme should be entertained in the presence of an unexplained and isolated increased enzyme activity. It prevents costly and unnecessary investigations.