What is the cause of Maria Barragan's persistent cough, given her past medical history (PMHx) of Hypertension (HTN), Hyperlipidemia (HLD), prediabetes, carotid body paraganglioma, and osteoporosis, and recent hospitalization for hypoxia related to Influenza and pneumonia, with current symptoms of a productive cough, postnasal drip, and normal oxygen saturation on room air?

Chronic Postnasal Drip: Given the patient's history of cough that worsens at night, productive cough with clear to yellow sputum, and presence of postnasal drip, this diagnosis is the most likely. The patient's symptoms and lack of systemic illness (e.g., fever) or other alarming features support this diagnosis.

Asthma or Chronic Obstructive Pulmonary Disease (COPD) Exacerbation: Although the patient is a never-smoker, asthma or COPD could still be considered, especially given the chronic nature of the cough and worsening at night. However, the lack of wheezing or other obstructive symptoms makes this less likely.
Gastroesophageal Reflux Disease (GERD): GERD can cause chronic cough, especially when lying down, due to acid reflux. The patient's history of laying down almost sitting up to alleviate symptoms could suggest GERD.
Chronic Bronchitis: This could be a consideration given the patient's history of productive cough, although the lack of smoking history and absence of other symptoms like wheezing make it less likely.

Lung Cancer: Although the patient is a never-smoker, lung cancer cannot be ruled out, especially given her age and history of carotid body paraganglioma (a type of neuroendocrine tumor). A negative chest X-ray does not entirely exclude lung cancer, and further imaging like a CT scan might be necessary if symptoms persist.
Pulmonary Embolism: This is a critical diagnosis to consider in any patient with chronic cough, especially if there are risk factors for thromboembolism. However, the patient's presentation and lack of other symptoms like chest pain or shortness of breath make this less likely.
Tuberculosis (TB): Although the patient denies any ill contact, TB is a diagnosis that should not be missed due to its potential severity. The chronic nature of the cough and presence of productive sputum could suggest TB, but the lack of systemic symptoms like fever, night sweats, or weight loss makes this less likely.

Bronchiectasis: This is a condition characterized by permanent dilation of parts of the airways, leading to chronic cough and sputum production. It is less common and would typically require further imaging like a CT scan for diagnosis.
Sarcoidosis: This is an autoimmune disease that can affect the lungs, among other organs, and cause chronic cough. However, it would typically be associated with other symptoms like shortness of breath, chest pain, or systemic illness, which are not present in this patient.