Macroamylasemia and other immunoglobulin-complexed enzyme disorders.

Macroamylase is a circulating complex of immunoglobulin linked to normal amylase in most cases. Its physical properties are heterogeneous, but its large size impairs renal filtration. Macroamylasemia usually causes hyperamylasemia and an amylase clearance:creatinine clearance (C(AM):C(CR)) ratio of less than 1 percent. Macroamylasemia occurs in 2.5 percent of hyperamylasemic patients, and 1 percent of apparently healthy subjects with normal amylase levels. It often accompanies diseases of aberrant immunity or conditions in which pancreatitis must be ruled out. This disorder should be considered in a patient with asymptomatic hyperamylasemia because its detection can obviate a prolonged diagnostic workup. The condition requires no treatment and may be transient. Macroamylasemia is one of several immunoglobulin-complexed enzyme (ICE) disorders. MacroLDemia, an ICE disorder of lactate dehydrogenase (LD), shares features with macroamylasemia. These and other ICE disorders appear to represent nonspecific dysproteinemic responses to disease.