Differential Diagnosis for Cough of 4 Weeks
Single Most Likely Diagnosis
- Postnasal drip syndrome: This is often the most common cause of a chronic cough, especially when it lasts for more than 3 weeks. It's usually due to allergic rhinitis, non-allergic rhinitis, or sinusitis, leading to the irritation of the upper airway and subsequent cough.
Other Likely Diagnoses
- Asthma: Cough can be a sole presenting symptom of asthma, especially in children. It's characterized by a dry, non-productive cough that may worsen at night or with exercise.
- Gastroesophageal reflux disease (GERD): Stomach acid reflux can irritate the throat and airways, leading to a chronic cough. This is more common in patients with a history of heartburn or those who experience cough after eating or at night.
- Chronic bronchitis: Part of chronic obstructive pulmonary disease (COPD), chronic bronchitis is characterized by a productive cough that brings up mucus, typically worse in the morning.
- Infections (e.g., pertussis, bronchitis): Though less common for a cough lasting exactly 4 weeks, certain infections can cause prolonged coughing.
Do Not Miss Diagnoses
- Lung cancer: Although less common, lung cancer can present with a persistent cough. It's crucial to consider this diagnosis, especially in smokers or those with a significant smoking history.
- Tuberculosis (TB): A chronic cough can be a symptom of pulmonary TB. It's essential to consider this diagnosis, especially in individuals who have been exposed to TB, have a weakened immune system, or have recently traveled to areas with high TB prevalence.
- Pneumonia: While typically presenting acutely, some forms of pneumonia (like mycoplasma pneumonia) can have a more insidious onset and prolonged course.
- Pulmonary embolism: Though usually presenting acutely, in some cases, a pulmonary embolism can cause a chronic cough, especially if it's recurrent or if there's associated pulmonary infarction.
Rare Diagnoses
- Cystic fibrosis: More commonly diagnosed in childhood, but can be diagnosed later in life, presenting with a chronic cough among other symptoms.
- Sarcoidosis: An autoimmune disease that can affect the lungs, causing a chronic cough among other symptoms.
- Eosinophilic pneumonia: A rare condition characterized by an accumulation of eosinophils in the lungs, which can cause a chronic cough.
- Foreign body aspiration: Though more common in children, adults can also aspirate foreign bodies, leading to a chronic cough if not diagnosed and treated promptly.