A 52-year-old man has had serum amylase of 450 to 600 U/L on three occasions over two months. He has no abdominal pain. Serum lipase is normal, and urinary amylase is low. Which is the most likely diagnosis?
- A Chronic relapsing pancreatitis
- B Parotitis with S-type hyperamylasemia
- C Macroamylasemia ✓
- D Ruptured ectopic pregnancy
Correct answer: C. Macroamylasemia
Explanation
In macroamylasemia, amylase binds immunoglobulin (usually IgG or IgA) to form a complex too large for glomerular filtration. The result is persistent benign hyperamylasemia with a LOW urinary amylase, since the macrocomplex cannot be cleared into urine. This combination of high serum amylase with reduced urinary amylase and normal lipase is diagnostic. In true pancreatitis both serum and urinary amylase are elevated and lipase parallels amylase.
Reference: Harper's Illustrated Biochemistry, 31st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.