Differential Diagnosis for Small Airway Disease on CT Scan

Single Most Likely Diagnosis

• Cystic Fibrosis: Although the patient has no known history of smoking or asthma, cystic fibrosis can cause small airway disease and bronchiectasis, which may be visible on a CT scan. The absence of smoking or asthma history does not rule out cystic fibrosis, as it is a genetic disorder.

Other Likely Diagnoses

• Chronic Obstructive Pulmonary Disease (COPD) without a smoking history: While less common, COPD can occur in non-smokers due to exposure to other pollutants or genetic predispositions. Small airway disease is a hallmark of COPD.
• Bronchiolitis Obliterans: This condition, characterized by inflammation and obstruction of the small airways, can occur without a history of smoking or asthma, often following a viral infection or as part of an autoimmune disorder.
• Idiopathic Pulmonary Fibrosis (IPF): Although IPF primarily affects the lung interstitium, it can also involve the small airways. The disease's progression and the patient's symptoms can sometimes lead to findings suggestive of small airway disease on imaging.

Do Not Miss Diagnoses

• Sarcoidosis: This autoimmune disease can affect any part of the body, including the lungs, and may cause small airway disease. It is crucial not to miss sarcoidosis due to its potential for significant morbidity if left untreated.
• Lymphangitic Carcinomatosis: Metastatic cancer can infiltrate the lymphatic vessels of the lung, leading to small airway obstruction and disease. This diagnosis is critical to identify due to its implications for cancer staging and treatment.
• Inhalational Injury or Exposure: Exposure to toxic substances can cause small airway disease. Identifying and managing such exposures is crucial for preventing further damage and treating the underlying condition.

Rare Diagnoses

• Neuroendocrine Cell Hyperplasia of Infancy (NEHI): A rare condition affecting infants, characterized by hyperplasia of neuroendocrine cells in the airways, leading to small airway disease.
• Follicular Bronchiolitis: An inflammatory condition affecting the small airways, often associated with autoimmune disorders or immunodeficiency states.
• Diffuse Panbronchiolitis: A rare condition characterized by chronic inflammation of the respiratory bronchioles, often associated with sinusitis and bronchiectasis.