Cryptogenic Organising Pneumonia (COP-BOOP)
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Cryptogenic Organising Pneumonia (COP-BOOP) Clinically resembles pneumonia. Worse prognosis when associated with rheumatoid arthritis.
ℹ️ About
- Also known as Bronchiolitis Obliterans with Organising Pneumonia (BOOP).
- Characterized by non-infective CXR infiltrates that mimic pneumonia but do not respond to antibiotics.
- Prognosis is worse when associated with underlying conditions such as rheumatoid arthritis.
🧬 Aetiology
- Characterized by the plugging of small airways and alveolar ducts with granulation tissue, leading to inflammation in the surrounding alveolar spaces.
- Organizing pneumonia occurs when there is abnormal repair of lung injury, leading to excessive proliferation of connective tissue.
Causes
- Infectious Causes: Can occur after viral infections like influenza, Mycoplasma, and adenovirus.
- Toxic Exposures: Inhalation of toxic fumes (e.g., nitrogen dioxide, chlorine, ammonia).
- Autoimmune and Connective Tissue Diseases: Associated with conditions like rheumatoid arthritis, systemic lupus erythematosus (SLE), and other collagen vascular diseases.
- Post-transplantation: Seen in bone marrow and lung transplant recipients as part of chronic graft-vs-host disease.
- Drug Reactions: May be triggered by medications such as penicillin and other drugs causing pulmonary inflammation.
🩺 Clinical Features
- Typically affects middle-aged males and females, with no significant gender preference.
- Presents with symptoms similar to pneumonia but without a clear infection source:
- Progressive fatigue and malaise.
- Persistent dry cough and increasing breathlessness.
- Flu-like symptoms, fever, and weight loss.
- Inspiratory crackles heard on lung auscultation.
🔎 Investigations
- Full Blood Count (FBC): normal white cell count, but the ESR may be significantly raised.
- Sputum Culture: Negative for pathogenic organisms.
- Chest X-ray (CXR): Shows patchy or diffuse shadowing, often bilateral. Unresponsive to antibiotic treatment.
- Pulmonary Function Tests (PFTs): a restrictive defect, some may have an FEV1/FVC ratio of < 70%.
- Arterial Blood Gas (ABG): type 1 respiratory failure in severe cases.
- High-Resolution CT (HRCT) of the Chest: Reveals air-space consolidation, often subpleural or peribronchial, and may show ground-glass opacities and bronchial wall thickening.
- Transbronchial Lung Biopsy: Histological findings include intra-alveolar buds of granulation tissue, consisting of intermixed myofibroblasts and connective tissue (Masson bodies).
💊 Management
- Treat Underlying Infection: though infections are not the primary cause of COP-BOOP.
- Remove Precipitants: Avoid known triggers such as toxic fumes or any identified environmental factors.
- Immunosuppressive Therapy: Oral corticosteroids (e.g., Prednisolone 0.5-1 mg/kg/day) are the mainstay of treatment, usually for 6-12 months, with a gradual tapering of the dose.
- Immunosuppressants: Consider additional immunosuppressive agents (e.g., azathioprine, methotrexate) if corticosteroid monotherapy is insufficient or if there are frequent relapses.
- Follow-Up: Regular monitoring of lung function and symptoms is necessary, with repeat HRCT scans if there is a lack of improvement or worsening of symptoms.
- Prognosis: Most patients respond well to corticosteroids, but relapses are common (about 30%), especially if tapering occurs too rapidly. Mortality rate is around 5%, typically associated with underlying conditions or severe disease.
Prognosis
- Most patients achieve good control with steroid therapy, but some may have residual lung scarring.
- Relapse rates are high, and about one-third of patients experience a return of symptoms after initial improvement.
- Worse outcomes are seen in those with underlying autoimmune conditions such as rheumatoid arthritis.
- Close follow-up is required, particularly during the steroid tapering phase, to monitor for signs of recurrence or adverse effects of prolonged immunosuppression.
References
3 Clinical Cases — Cryptogenic Organising Pneumonia (COP/BOOP) 🫁📋
- Case 1 — Subacute pneumonia-like illness 🦠: A 58-year-old woman presents with 6 weeks of cough, low-grade fever, malaise, and progressive breathlessness. She has received three courses of antibiotics with no improvement. CXR: patchy bilateral alveolar opacities, sometimes migratory. Teaching: COP often mimics non-resolving pneumonia. Key clue = failure to respond to antibiotics. Biopsy shows organising fibroblastic plugs (Masson bodies). Steroids usually produce dramatic clinical and radiological improvement.
- Case 2 — Post-viral organising pneumonia 🦠➡️🫁: A 44-year-old man develops increasing dyspnoea 3 weeks after an influenza-like illness. HRCT: peripheral and peribronchial patchy consolidations with ground-glass opacities. Teaching: COP may follow viral infection, drugs (e.g. amiodarone, methotrexate), or connective tissue disease. It presents subacutely and can resemble ILD or vasculitis. Corticosteroids are first-line; relapses are common but respond to retreatment.
- Case 3 — Chronic relapsing COP 🔄: A 65-year-old retired teacher treated with prednisolone for COP a year ago presents again with worsening cough and breathlessness. HRCT: new areas of consolidation, different from previous sites. Teaching: Relapsing COP is common (up to 50% relapse). Typically the opacities are migratory and resolve with repeat steroids. Long-term follow-up is required; a minority may progress to fibrosis.
