Macro-Gamma-glutamyltransferase as a possible cause of hyperenzymemia

Gamma-glutamyltransferase (GGT) is traditionally considered as a marker of liver and biliary tract diseases or alcohol consumption. However, in some cases, its persistent isolated increase is not accompanied by objective signs of hepatobiliary pathology, which requires an expansion of the differential diagnosis. The article presents a clinical case of an unexplained isolated significant increase in GGT levels with normal levels of other liver enzymes and minimal morphological changes in liver tissue, which made it possible to suspect the presence of macro-GGT. The diagnosis was confirmed by the method of deposition with polyethylene glycol 6000 (PEG 6000): the residual activity of GGT was 70.3%, which corresponds to the criterion of a macroenzyme. The detection of macro-GGT will help to avoid excessive diagnostic activity and unjustified correction of therapy. Thus, macro-GGT should be considered in the algorithm of differential diagnosis in patients with persistent isolated hyper-GGT in the absence of laboratory, instrumental and histological signs of liver pathology. A simple, affordable, and reproducible PEG deposition method can be used in routine laboratory practice to prevent diagnostic errors and unnecessary therapeutic interventions.