Department of Pediatrics, Golisano Children's Hospital, Upstate Medical University, Syracuse, NY, USA.
University of California and San Francisco, Department of Epidemiology and Biostatistics, San Francisco, CA, USA.
Pediatric Gastroenterology, Hepatology and Nutrition, Golisano Children's Hospital, Upstate Medical University, Syracuse, NY, USA.
Elevated enzyme activities in plasma may at times be attributed to the presence of macro-enzymes. The macro-enzymes are often serum enzymes in complex with immunoglobulins, resulting in a greater molecular mass that cannot be filtered by renal glomeruli and are, hence, retained in the plasma. The aspartate aminotransferase (AST) can exist as a macro-enzyme, although it has been rarely reported.
We describe a pediatric patient with persistently elevated serum AST activity, due to macro-enzyme formation between AST and an immunoglobulin. This is to highlight the importance of early diagnosis of macro-AST in an otherwise asymptomatic pediatric patient with isolated AST-elevation and to avoid unnecessary costly testing.