Differential Diagnosis for Coughing, Dizziness, Dyspnea on Exertion

Single Most Likely Diagnosis

• Chronic Obstructive Pulmonary Disease (COPD): This condition is characterized by chronic inflammation and airflow limitation in the lungs, leading to symptoms such as coughing, dyspnea on exertion, and potentially dizziness due to hypoxia or hypercapnia. The combination of these symptoms, especially in a patient with a history of smoking or exposure to lung irritants, makes COPD a highly plausible diagnosis.

Other Likely Diagnoses

• Asthma: Similar to COPD, asthma can cause coughing, dyspnea, and potentially dizziness if the asthma leads to significant hypoxia. Asthma is characterized by episodic airway constriction and inflammation, and symptoms can be triggered by exertion.
• Heart Failure: Heart failure, particularly left-sided, can lead to pulmonary congestion, resulting in cough and dyspnea on exertion. Dizziness can occur due to decreased cardiac output or arrhythmias associated with heart failure.
• Pulmonary Embolism (PE): While PE might not be the first consideration for chronic symptoms, recurrent small PEs or a large PE could present with exertional dyspnea, cough, and potentially dizziness due to hypoxia or decreased cardiac output.

Do Not Miss Diagnoses

• Pulmonary Hypertension: This condition involves high blood pressure in the arteries that supply blood to the lungs. It can lead to dyspnea on exertion, cough, and potentially dizziness due to decreased cardiac output or hypoxia. Pulmonary hypertension is critical to diagnose early due to its poor prognosis if left untreated.
• Cardiac Arrhythmias: Certain arrhythmias, such as atrial fibrillation, can lead to decreased cardiac output, resulting in exertional dyspnea and dizziness. A cough might not be a primary symptom but could occur if there's associated heart failure.
• Anemia: Severe anemia can cause dyspnea on exertion and dizziness due to decreased oxygen delivery to tissues. A cough might not be directly related but could be present if the anemia is due to chronic disease or conditions that also affect the lungs.

Rare Diagnoses

• Mitral Stenosis: A valvular heart disease that can lead to pulmonary congestion, resulting in cough, dyspnea on exertion, and potentially dizziness due to decreased cardiac output or arrhythmias.
• Lymphangitic Carcinomatosis: A condition where cancer spreads to the lymphatic vessels in the lungs, leading to cough, dyspnea, and potentially dizziness due to hypoxia.
• Sarcoidosis: An inflammatory disease that can affect the lungs, leading to cough, dyspnea, and potentially dizziness if there's significant pulmonary involvement or associated cardiac disease.

Each of these diagnoses requires careful consideration of the patient's history, physical examination, and diagnostic tests to determine the underlying cause of their symptoms.