Acute Bronchitis: This is often the most common cause of cough in adults, typically resulting from a viral upper respiratory infection. The justification for this diagnosis is the high prevalence of acute bronchitis in the general population and its association with cough as a primary symptom.

Chronic Obstructive Pulmonary Disease (COPD): Although more common in older adults, especially those with a smoking history, COPD can present in younger individuals, especially if they have a significant smoking history or exposure to lung irritants. The chronic nature of the cough and potential for wheezing or shortness of breath supports this diagnosis.
Asthma: Asthma can cause chronic cough, especially at night or with exercise, and is a common condition that can start at any age. Variability in symptoms and potential triggers (e.g., allergens, exercise) justify considering asthma.
Gastroesophageal Reflux Disease (GERD): GERD can cause cough due to the reflux of stomach contents into the esophagus, irritating the throat and lungs. This diagnosis is supported by symptoms such as heartburn, regurgitation, and cough that worsens with lying down or after eating.

Lung Cancer: Although less common in younger individuals, lung cancer can present with cough and would be catastrophic if missed. Risk factors such as smoking or exposure to carcinogens increase the likelihood.
Tuberculosis (TB): TB is a serious infection that can cause cough, fever, night sweats, and weight loss. Given its potential for severe consequences and transmission to others, it's crucial not to miss this diagnosis, especially in individuals with risk factors such as immunocompromised states or recent travel to endemic areas.
Pneumonia: Pneumonia can range from mild to life-threatening and presents with cough, fever, and shortness of breath. The potential for rapid progression and severe outcomes, especially in vulnerable populations, makes it a "do not miss" diagnosis.

Cystic Fibrosis: Although typically diagnosed in childhood, cystic fibrosis can present in adulthood, especially in individuals with a mild form of the disease. Chronic cough, recurrent respiratory infections, and malabsorption support this diagnosis.
Sarcoidosis: This autoimmune disease can cause cough, shortness of breath, and chest discomfort due to granulomatous inflammation in the lungs. It's considered rare but should be thought of in cases where common diagnoses are ruled out and systemic symptoms are present.
Bronchiectasis: A condition characterized by permanent enlargement of parts of the airways, often due to recurrent infections or inflammation. It can cause chronic cough, sputum production, and recurrent infections, making it a rare but important consideration in the differential diagnosis of chronic cough.