Gastroesophageal Reflux Disease (GERD): This is a common condition that can cause chronic cough, especially worse in the morning and at night, due to stomach acid reflux into the esophagus, irritating the throat and airways.

Postnasal Drip: Also known as upper airway secretion syndrome, this condition can cause a chronic cough due to the dripping of mucus from the back of the nose down into the throat, often worse at night.
Asthma: Although the patient has no history of respiratory conditions, asthma can develop at any age and may present with a chronic cough as the sole symptom, especially if it's cough-variant asthma.
Chronic Bronchitis: Part of chronic obstructive pulmonary disease (COPD), chronic bronchitis can cause a persistent cough, often worse in the morning, due to inflammation of the bronchial tubes.

Lung Cancer: Although less likely, lung cancer can present with a chronic cough as an early symptom. Given the potential severity, it's crucial not to miss this diagnosis, especially in a patient of this age group.
Pulmonary Embolism: While typically presenting with acute symptoms, some cases of pulmonary embolism can have a more chronic presentation, including a persistent cough. This is a life-threatening condition that must be considered.
Tuberculosis (TB): TB can cause a chronic cough and is a critical diagnosis not to miss due to its infectious nature and the need for prompt treatment.

Sarcoidosis: A condition characterized by the growth of granulomas (inflammatory cells) in various parts of the body, including the lungs, which can lead to a chronic cough.
Eosinophilic Pneumonia: A rare condition where eosinophils (a type of white blood cell) accumulate in the lungs, potentially causing a chronic cough among other symptoms.
Bronchiectasis: A condition where the airways of the lungs become abnormally widened, leading to a buildup of excess mucus that can cause a chronic cough.