Gastroesophageal Reflux Disease (GERD): This is often considered the most likely cause of chronic cough due to the high prevalence of GERD in the population and its known association with cough. GERD can cause cough through acid reflux into the esophagus, which can irritate the respiratory tract.

Asthma: Asthma is a common condition that can cause chronic cough, often accompanied by wheezing and shortness of breath. The cough in asthma can be dry or productive and is typically worse at night or with exercise.
Chronic Obstructive Pulmonary Disease (COPD): COPD, including chronic bronchitis and emphysema, is another likely cause of chronic cough. Patients with COPD often have a productive cough, especially in the morning, and may have a history of smoking.
Allergic Rhinitis: Allergic rhinitis can cause postnasal drip, leading to chronic cough. This condition is often associated with other allergic symptoms such as sneezing, runny nose, and itchy eyes.
Sinusitis: Chronic sinusitis can cause a chronic cough due to postnasal drip. Patients may also complain of facial pain, headache, and nasal congestion.

Lung Cancer: Although less common, lung cancer is a critical diagnosis not to miss. A chronic cough can be an early symptom, especially if it's a new cough in a smoker or someone with a significant smoking history.
Tuberculosis (TB): TB is another critical diagnosis that must be considered, especially in individuals who have been exposed to TB, have a weakened immune system, or have recently traveled to areas where TB is common.
Pulmonary Embolism: While less common as a cause of chronic cough, pulmonary embolism can present with a cough and is a life-threatening condition that requires immediate attention.
Heart Failure: Congestive heart failure can cause a chronic cough due to pulmonary congestion. This diagnosis is critical to identify due to its implications for cardiac function and overall prognosis.

Cystic Fibrosis: Although more commonly diagnosed in childhood, cystic fibrosis can present in adulthood with chronic cough among other symptoms like recurrent infections and malabsorption.
Sarcoidosis: This is a systemic disease that can affect the lungs and cause a chronic cough, among other symptoms like shortness of breath and chest pain.
Eosinophilic Granuloma with Polyangiitis (Churg-Strauss Syndrome): A rare autoimmune condition that can cause asthma, eosinophilia, and vasculitis, leading to chronic cough among other systemic symptoms.
Bronchiectasis: A condition characterized by damaged, dilated airways, leading to chronic cough and recurrent infections. It can be primary or secondary to other conditions like cystic fibrosis or immune deficiencies.