A Case of IgA-Binding-Type Macroamylasemia

Abstract

The serum amylase of an 83 year old man with no abdominal complaints, continuously high serum amylase activity and a remarkably low amylase clearance/creatinine clearance ratio was investigated and found to be IgA-binding type macroamylase. In electrophoresis of the serum amylase, a great majority of the phoretic band was in the globulin fraction. In Sephadex G-200 column gel chromatography, almost all amylase activity was found between the first and second protein peaks. When the patient's serum was acidified in vitro (pH 3.4), the amylase became normal in size and the change was reversible. The macroamylase was precipitated with anti-human IgA sheep serum. In enzymo-immunoelectrophoresis, amylase activity was found only in the IgA band. The urinary and salivary amylase in this patient was normal in size.