Rare Causes of Unexplained Chronic Cough in Adults.

Cough can result from a variety of etiologies, and rare pulmonary, otolaryngologic, cardiac, neurologic, medication-related, and functional conditions are often overlooked. Pulmonary etiologies, including structural airway abnormalities, endobronchial obstruction, expiratory central airway collapse, and occupational eosinophilic bronchitis, frequently require advanced imaging and bronchoscopy for diagnosis. Otolaryngologic conditions include elongated uvula, tonsillar hypertrophy, and external auditory canal pathology, which can trigger vagally mediated cough reflexes. Obstructive sleep apnea may result in chronic cough through inflammatory and reflux-mediated mechanisms. Cardiac causes include heart failure, airway compression, and arrhythmias. Neurologic, medication-induced, and functional causes should also be considered in refractory cases.