Differential Diagnosis for a 58-year-old man with progressive shortness of breath for 3 months

• Single most likely diagnosis
  • Chronic Obstructive Pulmonary Disease (COPD): This is a common condition in older adults, especially those with a history of smoking, leading to progressive shortness of breath due to airflow limitation.
• Other Likely diagnoses
  • Heart Failure: Progressive shortness of breath can be a symptom of heart failure, where the heart is unable to pump enough blood to meet the body's needs, leading to fluid buildup in the lungs.
  • Pneumonia or Recurrent Respiratory Infections: Repeated infections can lead to chronic symptoms, including shortness of breath, especially in individuals with compromised immune systems or underlying lung conditions.
  • Interstitial Lung Disease (ILD): A group of disorders that lead to scarring of lung tissue, causing progressive shortness of breath.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Pulmonary Embolism: Although less likely to cause progressive symptoms over months, a large or multiple pulmonary emboli could lead to chronic shortness of breath and would be critical to diagnose due to its high mortality rate if untreated.
  • Lung Cancer: While less common as a cause of progressive shortness of breath without other symptoms, lung cancer can cause obstructive symptoms or metastasize to the lungs, leading to respiratory distress.
  • Cardiac Tamponade: Accumulation of fluid in the pericardial space can compress the heart, severely impairing its function and leading to shortness of breath, among other symptoms.
• Rare diagnoses
  • Lymphangitic Carcinomatosis: A rare condition where cancer spreads to the lymphatic vessels in the lungs, causing shortness of breath.
  • Sarcoidosis: An autoimmune disease that can affect the lungs, leading to granulomatous inflammation and potentially causing shortness of breath.
  • Histoplasmosis or Other Fungal Infections: In endemic areas, chronic fungal infections can cause progressive lung disease and shortness of breath.