Yes, pepsin is a key component of gastric refluxate that can reach and damage the larynx
Pepsin is indeed a stomach enzyme that ascends with refluxate and causes direct laryngeal injury, even in the absence of acid. This represents a critical paradigm shift in understanding extraesophageal reflux (EER), as pepsin—not just acid—is now recognized as a primary mediator of laryngeal damage 1.
The Mechanism of Pepsin-Mediated Laryngeal Injury
The 2023 AGA guidelines explicitly acknowledge ongoing controversy about whether refluxate damage requires acidity or merely pepsin presence 1. Recent research has definitively answered this question:
- Pepsin remains stable and active up to pH 7, meaning it can cause damage even in non-acidic refluxate 2
- Pepsin is taken up by laryngeal epithelial cells through receptor-mediated endocytosis, creating a novel mechanism for cellular damage that persists even after the reflux episode 3
- At neutral pH (7.4), pepsin causes mitochondrial and Golgi complex damage, cell toxicity, and altered expression of stress-related genes 3
- Both weak acid and pepsin independently damage the laryngeal mucosal barrier, with pepsin acting as an independent factor for tissue injury 4
Clinical Implications
This pepsin-centric understanding explains several clinical observations:
Why PPIs Often Fail in EER
The guidelines note that EER symptoms show variable and often poor responses to PPI therapy 1. This makes sense because:
- PPIs only suppress acid production
- Pepsin remains active and damaging even when gastric pH is elevated
- Non-acidic reflux containing pepsin continues to reach and injure the larynx
The Real Components of Damaging Refluxate
When refluxate reaches the larynx, it contains 5:
- Acidic stomach contents
- Pepsin (the primary enzyme causing direct tissue damage)
- Bile acids
- Pancreatic enzymes
Diagnostic Considerations
Pepsin can be detected in saliva and exhaled breath condensate, offering novel diagnostic approaches 2, 6. However, the 2023 AGA guidelines note that salivary pepsin assays show poor concordance with esophageal reflux monitoring and overlap with healthy patients, limiting their clinical utility 1.
For patients with suspected laryngeal reflux:
- Look for laryngeal hoarseness, dysphonia, chronic cough, throat clearing, and globus sensation 1
- Consider pH-impedance monitoring to detect both acidic and non-acidic reflux events 1
- Recognize that 24-hour pH-impedance can identify weak-acidic (pH 4-7) and non-acidic (pH >7) reflux containing pepsin 1
Treatment Implications
The recognition of pepsin as the primary damaging agent opens new therapeutic avenues:
- Pepsin inhibitors (pepstatin, darunavir—an HIV protease inhibitor) suppress laryngeal inflammation and preserve mucosal integrity in animal models 7, 8
- Alginates may provide benefit by forming a barrier that "sieves" pepsin 1, 2
- Traditional PPIs address only the acid component, explaining their limited efficacy in many EER patients 1
Common Pitfall
Do not assume that lack of PPI response means reflux is not the problem. It may indicate that pepsin-mediated (rather than acid-mediated) injury is the dominant mechanism. The guidelines explicitly state that symptom improvement on PPIs may result from mechanisms other than acid suppression and should not confirm GERD 1.
The Bottom Line
Pepsin is not just "a component" of refluxate—it is the primary mediator of laryngeal injury in extraesophageal reflux. It damages tissue through direct cellular uptake, remains active at neutral pH, and explains why acid suppression alone often fails in treating laryngeal reflux symptoms. This understanding is driving development of pepsin-specific diagnostics and therapeutics, including direct pepsin inhibitors currently in clinical trials 8.