Gastrointestinal · Year 2 · from Gastrointestinal
Case 1: Lactose Intolerance
Patient Presentation
Demographics: 28-year-old Asian female
Chief Complaint: Abdominal bloating, cramping, and diarrhea after eating dairy products
History of Present Illness: The patient reports that over the past 2 years, she has noticed progressive intolerance to milk and dairy products. Within 30-60 minutes of consuming a glass of milk, she develops abdominal cramping, bloating, excessive gas, and watery diarrhea. Symptoms resolve within a few hours. She can tolerate small amounts of cheese and yogurt without symptoms. She has no weight loss, bloody stools, or nocturnal symptoms.
Past Medical History: None
Family History: Parents (originally from China) avoid milk due to similar symptoms
Physical Examination
- Vital Signs: Normal
- General: Well-appearing female in no distress
- Abdomen: Soft, non-tender, non-distended, normal bowel sounds
Workup and Results
- Lactose Hydrogen Breath Test: Baseline hydrogen 8 ppm; 2-hour post-lactose hydrogen 78 ppm (positive, >20 ppm rise indicates lactose malabsorption)
- CBC, CMP: Within normal limits
- tTG-IgA: Negative (rules out celiac disease)
Hydrogen breath test demonstrating a significant rise in breath hydrogen concentration after lactose ingestion, consistent with lactose malabsorption due to lactase deficiency.
Image Source: Clinical diagram adapted from educational materials
Diagnosis
Primary Lactose Intolerance (Adult-type Hypolactasia)
Clinical Correlation to Carbohydrate Digestion/Absorption
Lactose, the disaccharide in milk, must be cleaved by the brush border enzyme lactase into glucose and galactose for absorption. Lactase persistence (the ability to digest lactose in adulthood) evolved in populations with dairy traditions. Most of the world's population experiences lactase decline after weaning (the ancestral state). When undigested lactose reaches the colon, bacterial fermentation produces hydrogen (detected in breath), carbon dioxide, and short-chain fatty acids. The gas causes bloating and flatulence; the osmotic effect of unabsorbed lactose draws water into the lumen, causing diarrhea. Symptoms correlate with the dose of lactose consumed, which explains tolerance for aged cheeses (low lactose) and yogurt (bacterial lactase assists digestion).
Treatment
- Lactose avoidance or reduction to tolerable amounts
- Lactase enzyme supplements taken with dairy products
- Lactose-free dairy alternatives
- Calcium and vitamin D supplementation if dairy elimination affects intake
- Reassurance that this is not a disease but a normal genetic variant