A 24-year-old woman reports bloating, cramps and diarrhoea within hours of drinking milk, tolerated since childhood until her twenties. A lactose hydrogen breath test shows a rise in breath hydrogen of 25 ppm above baseline within 90 minutes accompanied by typical symptoms. What does this indicate?
- A Lactase non-persistence with carbohydrate malabsorption ✓
- B Small intestinal bacterial overgrowth
- C Irritable bowel syndrome with normal absorption
- D Sucrase-isomaltase deficiency
Correct answer: A. Lactase non-persistence with carbohydrate malabsorption
Explanation
In lactase deficiency, undigested lactose reaches the colon where bacteria ferment it to hydrogen, giving a breath hydrogen rise of 20 ppm or more above baseline within the test window, typically with reproduction of symptoms. An early hydrogen peak within 30 minutes suggests small intestinal bacterial overgrowth rather than colonic fermentation, which distinguishes it from this patient's pattern. Adult-type lactase non-persistence explains onset in adulthood.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.