Increase of serum lactate dehydrogenase caused by a macroenzyme. A case report.

Macroenzymes, complexes of serum enzymes with a plasma protein, are able to cause falsely increased total serum enzyme levels. We report the case of a patient presenting with an isolated increase of serum lactate dehydrogenase (LDH) activity due to the presence of a complex of LDH with an immunoglobulin, identified as IgG kappa. Before the macroenzyme responsible for the LDH elevation was detected, the patient underwent extensive diagnostic procedures, including splenectomy. Awareness of this phenomenon could prevent unnecessary, invasive and costly investigations.