Macro enzymes: prevalence, composition, detection and clinical relevance.

The presence of a macro enzyme, i.e. an enzyme with an abnormally high molecular weight, frequently leads to a genuinely increased serum activity or an interference in laboratory assays. This may thereby result in false positive diagnoses, such as acute myocardial infarction or pancreatitis. The various forms of macro enzymes are reviewed. In the case of immune complexes the immunoglobulins and (iso)-enzymes involved are discussed, as well as the specificity of the interaction, the prevalence and clinical relevance, associations with autoimmune or other diseases, and their behaviour in laboratory assays.