Macroenzymes are serum enzymes that have a higher molecular mass than the corresponding enzyme normally found in serum under physiologic or pathophysiologic conditions. Although no evidence convincingly indicates that macroenzymes cause disease or necessitate treatment, some patients with immunoglobulin-complexed enzyme disorders have previously been reported to have associated autoimmune diseases or malignant lesions. To address this issue, we reviewed the medical records of 42 patients in whom a macroenzyme had been detected during assessment at the Mayo Clinic between 1986 and 1990. Of these 42 patients, 21 had macro-creatine kinase, 10 had macro-lactate dehydrogenase, 6 had macro-aspartate aminotransferase, and 5 had macroamylase in the serum. Although the study group did not include all Mayo patients with this phenomenon, it represented a sufficient sample size to determine retrospectively whether specific dismissal diagnoses were present concurrently. The most common findings in this group of patients with macroenzymes were (1) advanced age (except for those with macro-aspartate aminotransferase), (2) cardiovascular disease (probably due to sampling bias), (3) malignant lesions (particularly in those with macro-creatine kinase), and (4) rheumatologic disease (in those with macro-lactate dehydrogenase). The immunoglobulin-complexed enzyme disorders are characterized by increased total serum enzyme levels that are often isolated and persistent. Physicians should be aware of the presence of macroenzymes so that invasive or costly procedures are not undertaken unnecessarily to determine the cause of increased serum enzyme levels.
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