Unexplained High Activity of Aspartate Aminotransferase in an Asymptomatic Pediatric Patient

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.