Asthma
Upper airway cough syndrome (Postnasal drip)
Gastroesophageal reflux disease (GERD)
Environmental triggers
Pneumonia (chronic, persistent)
Pneumonia ((recurrent/chronic aspiration)
Bronchitis (due to a protracted bacterial infection)
Noninfective bronchitis (due to tobacco smoke, etc)
Bronchiectasis; chronic suppurative lung disease
Eosinophilic lung disease
Medications (ACE-I, PPIs, etc, Interstitial lung disease from meds)
Foreign body (in younger children)
Interstitial lung disease
Mechanical inefficiency: tracheobronchomalacia, primary ciliary dyskinesia, etc.
Congenital abnormality
Space-occupying lesions (cysts and tumors)
Pertussis
Postinfectious bronchospasm
Cystic fibrosis
Immunodeficiency
Cardiac
Upper airway pathology (OSA, chronic sinusitis)
Ear disease (Oto-respiratory reflex (Arnold’s reflex), in which stimulation of the auricular branch of the vagus nerve triggers cough)
Esophageal disorders
Tic cough (habit cough) / Tourette syndrome.
Psychogenic cough
Thinking through the Differential Diagnosis
The DDx may be categorized into pulmonary causes and extrapulmonary causes. Pulmonary causes are infectious and non-infectious.
Further Reading
Allergy Asthma Proc. 2014 Mar-Apr;35(2):95-103. Differential diagnosis of chronic cough in children. https://www.ncbi.nlm.nih.gov/pubmed/24717785
Am Fam Physician. 2017 Nov 1;96(9):575-580. Chronic Cough: Evaluation and Management. https://www.aafp.org/afp/2017/1101/p575.html
Am Fam Physician. 2011 Oct 15;84(8):887-892. Evaluation of the Patient with Chronic Cough. https://www.aafp.org/afp/2011/1015/p887.html