Pulmonary fibrosis

Progressive scarring of the lung interstitium (fibrosis) leading to restrictive lung disease and impaired gas exchange; often idiopathic (when termed IPF) with a characteristic UIP histopathologic pattern.

• Pulmonary fibrosis (especially IPF) has a poor prognosis (median survival ~3–5 years). Early recognition and treatment can slow decline. It's frequently tested for its classic findings (Velcro crackles, clubbing, honeycombing on CT) and as a prototype for interstitial lung diseases.

• Insidious onset of dyspnea on exertion and dry cough over months to years (usually age >50). Exam: fine 'Velcro' crackles at the lung bases and often digital clubbing. Patients typically lack wheezing or sputum production (distinguishing from COPD).
• Advanced disease: may have resting hypoxemia, cyanosis, or signs of pulmonary hypertension (e.g., loud P2, peripheral edema from cor pulmonale).
• Secondary causes to look for: autoimmune diseases (e.g., rheumatoid arthritis, scleroderma), chronic occupational or environmental exposures (silica, asbestos, moldy organic dust in farmers/bird handlers), or medications (amiodarone, bleomycin, nitrofurantoin, etc.). If a specific cause is identified, the fibrosis is considered secondary (not idiopathic).

1. Evaluate for alternative causes in anyone with suspected pulmonary fibrosis: detailed exposure history (occupational, environmental) and serologies for connective tissue disease. If a cause is found (e.g., silica, scleroderma), manage that underlying disorder rather than labeling it IPF.
2. Obtain a high-resolution CT (HRCT) of the chest in all patients. A UIP pattern on HRCT (subpleural, basal-predominant fibrosis with reticular opacities and honeycombing ± traction bronchiectasis) strongly suggests IPF in the right clinical context.
3. Perform pulmonary function tests: expect a restrictive pattern (reduced FVC, TLC with normal or high FEV₁/FVC) and markedly reduced DLCO (diffusing capacity). Exertional desaturation is common as fibrosis progresses.
4. If the diagnosis remains unclear or HRCT is indeterminate, consider a surgical lung biopsy for definitive histopathology. UIP histology (patchy interstitial fibrosis with alternating normal lung, fibroblast foci, and honeycombing) confirms idiopathic pulmonary fibrosis.
5. Assess disease severity (oxygen needs, PFT trends) and refer to specialized centers early if advanced. A multidisciplinary discussion (pulmonologist, radiologist, pathologist) is often used to finalize the diagnosis.

1. Antifibrotic therapy (e.g., pirfenidone, nintedanib) can slow the decline in IPF lung function.
2. Supportive care is crucial: supplemental oxygen for hypoxemia, pulmonary rehabilitation, and management of symptoms. Also ensure smoking cessation and up-to-date vaccinations.
3. If an underlying cause is identified, treat it (e.g., immunosuppressants for autoimmune disease, removal from exposure in pneumoconiosis). Avoid offending drugs.
4. Lung transplantation offers the best chance of long-term survival in advanced pulmonary fibrosis and is indicated for eligible patients with progressive disease.

• Velcro crackles + clubbing in a patient with chronic dyspnea should prompt consideration of IPF (about half of IPF patients have clubbing). Clubbing is rarely seen in purely obstructive lung diseases like COPD.
• Common drug causes of pulmonary fibrosis: chemotherapy agents (e.g., bleomycin, busulfan), certain antiarrhythmics (amiodarone), chronic nitrofurantoin use, and other drugs (e.g., methotrexate). Always review medications in ILD patients.
• Classic UIP pathology (seen in IPF): patchy areas of normal lung alternating with dense fibrosis (temporal heterogeneity) plus fibroblastic foci and end-stage honeycomb change. This distinguishes IPF/UIP from other patterns like NSIP (which has more uniform fibrosis).

• Sudden acute exacerbation of IPF (rapid worsening dyspnea with new diffuse ground-glass infiltrates on imaging) – often leads to respiratory failure and has high mortality. Requires urgent care and often hospitalization.
• Signs of advanced disease: e.g., needing oxygen at rest, hypercapnia, or evidence of cor pulmonale (JVD, edema). These indicate end-stage fibrosis – prompt evaluation for transplant or palliative measures is warranted.

1. Chronic exertional dyspnea + basilar crackles → suspect interstitial lung disease (consider PF).
2. First, exclude other etiologies: review medications, occupational exposures, and test for connective tissue diseases.
3. High-resolution CT chest is the key diagnostic step: if a UIP pattern is seen and no alternative cause is found, IPF can be diagnosed without biopsy.
4. If HRCT is atypical or suggests another process, pursue further evaluation (e.g., bronchoscopy or surgical lung biopsy) for definitive diagnosis.
5. Once diagnosis is confirmed, initiate appropriate therapy (antifibrotics for IPF, or cause-specific treatment) and monitor lung function; refer early for transplant evaluation in rapidly progressive cases.

• A 68‑year‑old male with a 1-year history of progressive exercise intolerance and dry cough. He has bilateral basal inspiratory crackles and digital clubbing on exam. Pulmonary function testing shows a restrictive pattern with reduced DLCO. High-resolution CT of the lungs reveals bibasilar subpleural reticular opacities and honeycombing. → Idiopathic pulmonary fibrosis (usual interstitial pneumonia pattern).
• Open lung biopsy in a patient with chronic interstitial lung disease shows patchy interstitial fibrosis with fibroblast foci and honeycombing, alternating with areas of relatively normal lung. → Usual interstitial pneumonia pattern consistent with IPF.