Differential Diagnosis for a 71-year-old Male with Chronic Cough and Smoking History

Single Most Likely Diagnosis

• Chronic Bronchitis: Given the patient's smoking history and chronic cough, chronic bronchitis is a highly likely diagnosis. The CT scan shows well-aerated pulmonary parenchyma and an unremarkable airway, which is consistent with chronic bronchitis, especially in the absence of significant airspace disease or other parenchymal abnormalities.

Other Likely Diagnoses

• Pulmonary Fibrosis: Although the CT scan does not show significant fibrosis, the minimal left lower lobe soft tissue density pulmonary nodularity could be an early sign of pulmonary fibrosis, especially in a smoker. However, the lack of more extensive findings makes this less likely than chronic bronchitis.
• Bronchiectasis: This condition could also present with chronic cough in a smoker. However, the CT scan would typically show more pronounced bronchial dilatation, which is not mentioned here.
• COPD (Chronic Obstructive Pulmonary Disease): This is a broad category that includes chronic bronchitis and emphysema. The patient's symptoms and smoking history are consistent with COPD, but the CT scan does not specifically show emphysematous changes.

Do Not Miss Diagnoses

• Lung Cancer: Although the CT scan mentions a minimal left lower lobe soft tissue density pulmonary nodule (0.3 cm), any nodule in a smoker warrants careful consideration for malignancy. Even small nodules can be cancerous, and follow-up or further investigation (e.g., PET scan, biopsy) may be necessary.
• Pulmonary Embolism: This condition can present with cough among other symptoms. Although the CT scan does not show signs suggestive of pulmonary embolism (e.g., filling defects in pulmonary arteries), it's crucial to consider this diagnosis due to its high mortality if missed.

Rare Diagnoses

• Sarcoidosis: This condition can cause pulmonary nodules and cough. However, it would typically present with more widespread lymphadenopathy and parenchymal involvement, which is not described in the CT scan.
• Lymphangitic Carcinomatosis: This rare condition involves the spread of cancer through the lymphatic vessels of the lung and can cause cough and nodular patterns on imaging. However, it is much less likely given the minimal findings on the CT scan and the absence of known primary cancer.
• Idiopathic Pulmonary Fibrosis (IPF): While IPF can present with cough and pulmonary nodules, it typically shows more extensive fibrotic changes on CT scans, which are not present in this case.