Abstract

Hyperamylasaemia with low or normal urinary amylase excretion in the face of normal renal function has been noted to be indirect evidence for the existence of macroamylasaemia. A more refined indicator is a low ratio of renal amylase clearance to creatinine clearance. This report describes observations made in three patients, each of whom displayed the indirect features suggestive of macroamylasaemia. In none of these patients, however, could a serum macroamylase be demonstrated by chromatography. Ultracentrifugation was also done in one of the patients and likewise failed to disclose a macroamylase in the serum. When the isozyme nature of the serum amylase in each of these patients was examined, there was found to be a marked rise in activity of the salivary-type isoamylase (`S-type amylase'). The pancreatic-type isoamylase (`P-type amylase') was normal in one patient and perhaps slightly above normal in the other two. These data indicate that (1) S-type hyperamylasaemia may exhibit the indirect criteria taken to indicate macroamylasaemia and thereby simulate the latter disorder; and (2) unequivocal identification of macroamylasaemia requires the direct demonstration of the presence in the serum of a macromolecular amylase complex.