What is the cause of a 52-year-old woman's persistent dry cough, which began 8 weeks ago with a cold and sore throat, despite using Flonase (fluticasone) and Benzonatate (benzonatate), with a history of allergic rhinitis and no evidence of acute cardiopulmonary abnormality on chest x-ray?

Differential Diagnosis for a 52-year-old Woman with an 8-week Dry Cough

• Single most likely diagnosis:
  • Postnasal drip syndrome (also known as upper airway secretion syndrome): This is the most likely diagnosis given the patient's history of allergic rhinitis, symptoms of phlegm in the throat, and a dry cough that started with a cold/sore throat. The fact that Flonase (a nasal steroid) and benzonatate (a cough suppressant) provide some relief also supports this diagnosis.
• Other Likely diagnoses:
  • Chronic rhinitis: Given the patient's history of allergic rhinitis, it's possible that her symptoms are related to chronic inflammation of the nasal passages, leading to postnasal drip and cough.
  • Sinusitis: The patient's symptoms of dry cough, sore throat, and feeling of phlegm in the throat could be related to chronic sinusitis, especially if her allergic rhinitis is not well-controlled.
  • Sleep-related cough: The patient's history of snoring and waking up with a sore throat suggests that sleep-related factors, such as sleep apnea or acid reflux during sleep, could be contributing to her cough.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed):
  • Lung cancer: Although the patient's chest X-ray was normal, it's essential to consider lung cancer in any patient with a persistent cough, especially if they have a history of smoking (not mentioned in this case).
  • Pulmonary embolism: Although the patient's symptoms do not strongly suggest pulmonary embolism, it's a potentially life-threatening condition that should be considered in any patient with a persistent cough, especially if they have risk factors such as immobility or cancer.
  • Tuberculosis: Although less likely, tuberculosis should be considered in any patient with a persistent cough, especially if they have been exposed to someone with TB or have a weakened immune system.
• Rare diagnoses:
  • Sarcoidosis: This is a rare condition that can cause a persistent cough, among other symptoms. It's characterized by the growth of granulomas in various parts of the body, including the lungs.
  • Eosinophilic pneumonia: This is a rare condition characterized by the accumulation of eosinophils in the lungs, leading to inflammation and cough.
  • Habit cough: This is a rare condition where the cough is a habitual behavior, often seen in children but can occur in adults as well.