Idiopathic Pulmonary Fibrosis

Related Subjects: | Idiopathic Pulmonary Fibrosis | Diffuse Parenchymal Lung disease | Asbestos Related Lung disease | Sarcoidosis | Coal Worker's Pneumoconiosis | Silicosis | Farmer's Lung | Cryptogenic Organising Pneumonia (COP-BOOP) | Extrinsic Allergic alveolitis (Hypersensitivity) | Byssinosis | Pneumoconiosis | Cor Pulmonale |Chest X Ray Interpretation

O2 sats run low
Lung sounds harsh like ripped Velcro
Nail tips swollen, bowed
Bird, rheum, dust free history
Honeycombs high res CT      Link to author

About

• Previously Cryptogenic Fibrosing Alveolitis
• Diffuse Parenchymal lung disease of unknown aetiology
• Progressive fibrosis of alveoli and interstitium forming a Honeycomb lung
• An acute form - Hamman-Rich syndrome

Epidemiology

• Cigarette smoking, exposure to wood or metal dust.
• Commoner in women, Age usually over 50
• Associated increased risk of lung cancer

Pathophysiology

• Very poorly understood genetic and histological findings
• A mutant telomerase is associated with familial idiopathic pulmonary fibrosis
• Variant of a Gene for mucin 5B (MUC5B) x 14 commoner in IPF
• Alveolar epithelial cells release potent fibrogenic cytokines and growth factors.
• Increased Tumour necrosis factor (TNF), transforming growth factor, platelet-derived growth factor, Insulin-like growth factor-1, and endothelin-1 (ET-1).
• Migration and proliferation of fibroblasts and the transformation of fibroblasts into myofibroblasts which secrete extracellular matrix proteins.

Histology

• Usual interstitial pneumonia : patchy fibrosis ? honeycomb lung. Fibrosis > Inflammation
• Desquamative interstitial pneumonia : macrophages, lymphoid aggregates. Inflammatory.
• Ground glass on HRCT and steroid-responsive.

Clinical

• Slowly progressive breathlessness with dry cough
• Gradually decreasing exercise tolerance
• Weight loss, tiredness and cough and breathlessness develop over 6 months.
• Haemoptysis is rare - think tumour or embolism
• Fine inspiratory "Velcro" crackles
• Finger clubbing is seen in 50% (also seen in Asbestosis)
• Eventual pulmonary hypertension and cor pulmonale

Differentials

• Occupational lung diseases
• Sarcoidosis, Scleroderma
• Lymphangitis carcinomatosa
• Allergic: Exposure to birds and pets, Drug or family history
• Miliary tuberculosis
• Radiation pneumonitis
• Histoplasmosis
• Drugs e.g. Busulphan, Paraquat
• Coccidiodomycosis
• Histiocytosis X
• Rheumatoid lung disease

Investigations

• FBC - ? Hb polycythaemia, U&E
• Pulmonary function tests: progressive restrictive (small lungs) defect on PFT and Reduced Diffusing capacity for carbon monoxide (DLco)
• ABG: hypoxaemia (Type 1 RF) which is often exaggerated or elicited by exercise and low/normal arterial CO2 levels.
• 30% have Rheumatoid factor +ve or ANA +ve
• CXR: diffuse bilateral basal reticulonodular shadowing. Progressive fibrosis and is less steroid-responsive
• HRCT allows differentiation into Usual interstitial pneumonia (UIP) there is progressive fibrosis and honeycomb lung formation and is poorly responsive to steroids. In Diffuse Interstitial Pneumonitis which shows "ground glass appearance" and is very steroid-responsive
• Lung biopsy may be considered in occasional cases but not with out potential complications

Complications

• Progressive Type 1 RF
• Cor pulmonale and pulmonary hypertension
• Chest infective exacerbation
• Death from respiratory failure
• Lung cancer is increased

Improved prognostic indicators

• Young female, steroid-responsive
• Ground glass HRCT appearance and DIP Histology

Management

• If the Vital capacity is between 50-80-% predicted then patients may be considered for the antifibrotic agent Pirfenidone or the Tyrosine kinase inhibitor Nintedanib
• Smoking cessation. Exercise as tolerated
• Medications for GORD can reduce the cough
• Influenza and Pneumococcal vaccination
• Early use of antibiotics for infective episodes.
• Single Lung transplantation in selected cases but risks of developing lung cancer
• Median survival 2.8 years. Home oxygen. Palliation.