A 9-year-old boy presents with fever and painful bilateral parotid swelling. Serum amylase is 420 U/L but serum lipase is normal. The source of the elevated amylase is:

• A Pancreatic acinar cells releasing P-type amylase
• B Salivary glands releasing S-type amylase ✓
• C Intestinal brush border releasing isoamylase
• D Fallopian tube epithelium releasing ovarian-type amylase

Explanation

Mumps parotitis injures salivary acinar cells, releasing the S-type (salivary) isoenzyme of amylase into serum. Pancreatic amylase is the P-type isoenzyme, and pancreatic pathology would raise lipase in parallel because lipase is pancreas-specific. The normal lipase here excludes acute pancreatitis and confirms a non-pancreatic source. Intestinal and tubal sources contribute negligibly to serum amylase in this setting.

Reference: Harper's Illustrated Biochemistry, 31st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.