A 38-year-old woman undergoes routine health screening. Her serum amylase is 320 U/L and has remained between 280 and 350 U/L across three measurements over six months. She has no abdominal pain, her serum lipase is normal, ultrasound abdomen is normal, and her urinary amylase excretion is disproportionately low relative to serum levels. The most likely diagnosis is:

• A Macroamylasemia ✓
• B Chronic pancreatitis
• C Parotitis
• D Renal insufficiency

Explanation

In macroamylasemia, amylase binds to immunoglobulin or other macromolecules forming complexes too large to be filtered by the glomerulus, so serum amylase persists at elevated levels while urinary amylase is disproportionately low. The benign course, normal lipase, and absent symptoms exclude pancreatitis. Renal failure can raise serum amylase, but it would elevate urea and creatinine and does not produce selectively low urinary amylase clearance in this isolated fashion.

Reference: Tietz Fundamentals of Clinical Chemistry, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.