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Patients with chronic cough hypersensitivity syndrome have a negative workup and lack of response to common treatments and are characterized by having a sensation of a tickle or itch in the throat, as well as being sensitive to triggers such as cold air, eating, and odors.
The etiologies of chronic cough are numerous and may include pathology from the nose and nasopharynx to the distal bronchial tree.
Additional specialists also important in the workup include the gastroenterologist, allergist and immunologist, neurologist, and speech therapist.
The trigeminal, glossopharyngeal, and vagus nerves supply the afferent pathways for cough receptors; the vagus, through its pharyngeal, superior laryngeal, and pulmonary branches, supplies the large majority of these receptors.
Eosinophilic airway diseases have airway inflammation due to eosinophils, which can be diagnosed by raised induced sputum eosinophil counts and increased exhaled nitric oxide levels.
They are also associated with good steroid responsiveness.
This cough reflex has been shown to have neuroplasticity such that a hypersensitive response is elicited over time due to the cough itself inducing chronic irritation and inflammation and tissue remodeling.
If the chest radiograph findings are abnormal, further workup depends on the specific finding.
Chest CT scan, bronchoscopy, needle biopsy, and sputum studies are all potentially warranted studies if a pulmonary lesion is found.
For the immunocompetent nonsmoker who does not use ACE inhibitors and has normal chest radiograph findings, a systematic approach to the most common causes of chronic cough is warranted, keeping in mind that more than one cause may be present.
Further compounding this is the fact that oftentimes more than one condition is simultaneously present.
A fourth etiology that deserves mention is nonasthmatic eosinophilic bronchitis (NAEB), which is relatively common, easy to diagnose and treat, and should be considered early on in the diagnostic evaluation.