Differential Diagnosis for Chronic Cough
Single Most Likely Diagnosis
- Chronic Postnasal Drip: This is often the most common cause of chronic cough, especially when other symptoms like nasal congestion or a sensation of postnasal drip are present. The cough can be persistent and is usually worse when lying down.
Other Likely Diagnoses
- Asthma: Even without wheezing, asthma can cause a chronic cough, especially at night or with exertion. A negative chest X-ray does not rule out asthma.
- Gastroesophageal Reflux Disease (GERD): Stomach acid reflux can irritate the throat and cause a chronic cough. Symptoms may include heartburn, but some patients with GERD-induced cough may not experience typical reflux symptoms.
- Allergic Rhinitis: Similar to chronic postnasal drip, allergies can lead to chronic cough due to the constant irritation of the nasal passages and subsequent postnasal drip.
Do Not Miss Diagnoses
- Lung Cancer: Although less likely in a patient with a negative chest X-ray, lung cancer can present with a chronic cough as an early symptom. Risk factors such as smoking history increase the concern.
- Tuberculosis (TB): A chronic cough can be a symptom of TB, especially in individuals who have been exposed or are from areas with high TB prevalence. A negative chest X-ray does not completely rule out TB, especially in early or extrapulmonary disease.
- Pulmonary Embolism: While typically presenting acutely, some cases of pulmonary embolism can have a more chronic presentation, including a persistent cough. This is a critical diagnosis not to miss due to its high mortality rate if untreated.
Rare Diagnoses
- Sarcoidosis: This autoimmune disease can cause a chronic cough among other symptoms, due to granulomatous inflammation in the lungs. It's less common but should be considered in the differential, especially with systemic symptoms.
- Eosinophilic Bronchitis: Not related to asthma, this condition involves eosinophilic inflammation of the airways, leading to a chronic cough without wheezing or airway hyperresponsiveness.
- Habit Cough: A psychogenic cough that can be persistent and is often seen in children but can also occur in adults. It's usually characterized by its honking or barking quality and resolves with suggestion therapy.