What is Upper Airway Cough Syndrome?
Upper Airway Cough Syndrome (UACS)—formerly called postnasal drip syndrome—is a clinical condition in which chronic cough results from mechanical or inflammatory stimulation of cough receptors in the hypopharynx and larynx by secretions draining from the nose and sinuses. 1, 2
Definition and Terminology
The American College of Chest Physicians recommends using "Upper Airway Cough Syndrome" rather than "postnasal drip syndrome" because it more accurately reflects the underlying pathophysiology of chronic cough related to upper airway abnormalities. 2
UACS is the single most common cause of chronic cough in adults, accounting for approximately 18.6%–81.8% of chronic cough cases, either alone or in combination with other conditions. 1, 2
Together with asthma and gastroesophageal reflux disease, UACS accounts for roughly 90% of chronic cough cases in nonsmokers with normal chest radiographs who are not taking ACE inhibitors. 1, 3
Pathophysiology
The primary mechanism is mechanical stimulation of cough receptors in the hypopharynx or larynx by nasal and sinus secretions that drain posteriorly. 2, 4
Patients with UACS exhibit increased sensitivity of the upper airway cough reflex compared with healthy individuals, contributing to symptom severity. 2, 4
The cough in UACS patients is likely due to hypersensitivity of either the upper airways sensory nerve, lower airways sensory nerve, or a combination of both. 4
Alternative mechanisms include chemical irritation of afferent cough pathways and possible aspiration of secretions stimulating lower airway receptors, though supporting data are limited. 2
Clinical Presentation
Typical Symptoms
Sensation of drainage into the throat (though absent in approximately 20% of patients). 1, 2
Nasal discharge or congestion. 2
Tickle sensation in the throat. 2
History of recent upper respiratory infection. 2
Physical Examination Findings
Cobblestone appearance of the oropharyngeal mucosa is a hallmark finding, though relatively sensitive but not specific. 1, 2
Visible mucoid or mucopurulent secretions in the oropharynx or posterior pharynx. 1, 2
Mucopurulent secretions may be observed on nasopharyngeal examination. 2
Critical Diagnostic Considerations
No objective test can confirm UACS; the condition cannot be quantified by measuring postnasal drip or directly proving causality. 2
Approximately 20% of patients have "silent" UACS with no obvious symptoms of postnasal drainage yet still respond to treatment. 1, 2
The pivotal diagnostic criterion is improvement or resolution of cough after a targeted therapeutic trial with first-generation antihistamine plus decongestant. 1, 2
Cough characteristics (productive vs. non-productive, timing, or quality) should not be used to rule in or rule out UACS because they are unreliable and non-specific. 1, 2
The absence of classic upper airway symptoms does not exclude UACS. 2
Common Underlying Causes
Allergic rhinitis accounts for approximately 28% of UACS cases. 1, 5
Non-allergic rhinitis (including vasomotor rhinitis and NARES) is the most common upper airway disease associated with UACS, accounting for approximately 59% of cases. 1, 5
Chronic rhinosinusitis accounts for approximately 31% of UACS cases and may cause throat mucus sensations even when classic sinus pain or pressure are absent. 1
Post-infectious rhinitis following an upper respiratory tract infection. 1
Common Pitfalls to Avoid
Do not rely on physical examination findings alone; the absence of visible posterior pharyngeal drainage or cobblestoning does not rule out UACS. 1
Do not assume that lack of upper airway symptoms excludes UACS; up to 20% of patients have a silent presentation. 1, 2
Do not use cough characteristics to differentiate UACS from other causes of chronic cough. 1, 2
Do not overlook "silent" UACS as a potential cause of chronic cough before investigating less common etiologies. 1
GERD frequently mimics UACS with upper respiratory symptoms and may coexist with postnasal drip. 1