Macro-aspartate aminotransferase mimicking hepatic injury: a diagnostic dilemma for clinicians.

Chronic isolated elevated liver enzymes could be a sequela of macroenzymes, causing diagnostic confusion. We presented the case of an elderly female with no prior history of chronic liver disease who was referred by her primary oncologist for evaluation of persistently elevated aspartate aminotransferase (AST) since her lung cancer diagnosis. Her autoimmune and hepatitis work-up was negative. AST remained elevated despite discontinuing chemotherapy, and a repeat chronic liver disease work-up was unrevealing. Macro-AST was suspected and confirmed using the polyethylene glycol precipitation method. This case highlighted that clinicians should suspect macroenzymes in appropriate clinical settings to avoid patients' anxiety related to invasive and unnecessary testing.