Makindo Medical Notes

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

About

• Previously known as Cryptogenic Fibrosing Alveolitis.
• A diffuse parenchymal lung disease of unknown aetiology.
• Characterized by progressive fibrosis of the alveoli and interstitium, forming a "honeycomb lung."
• An acute form known as Hamman-Rich syndrome may occur.

Epidemiology

• Risk factors include cigarette smoking, exposure to wood or metal dust.
• More common in women; usually affects individuals over 50 years old.
• Associated with an increased risk of lung cancer.

Pathophysiology

• Genetic predispositions and abnormal fibrotic processes are not fully understood.
• Mutations in the telomerase gene have been associated with familial IPF.
• Variants in the MUC5B gene are more common in idiopathic pulmonary fibrosis (IPF).
• Alveolar epithelial cells release potent fibrogenic cytokines and growth factors, leading to fibroblast proliferation.
• Key factors include TNF, TGF-β, PDGF, IGF-1, and ET-1.

Histology

• Usual Interstitial Pneumonia (UIP): Patchy fibrosis with honeycomb changes; more fibrosis than inflammation.
• Desquamative Interstitial Pneumonia (DIP): Characterized by macrophages and lymphoid aggregates; more inflammatory, with "ground glass" on HRCT and better response to steroids.

Clinical

• Slowly progressive dyspnoea and dry cough.
• Decreasing exercise tolerance, weight loss, and fatigue over six months.
• Fine inspiratory "Velcro" crackles on auscultation.
• Finger clubbing in 50% of cases (also seen in asbestosis).
• Haemoptysis is rare—consider other causes like tumour or embolism if present.
• Progression leads to pulmonary hypertension and cor pulmonale.

Differentials

• Occupational lung diseases (e.g., asbestosis, silicosis).
• Sarcoidosis, scleroderma, and other connective tissue diseases.
• Lymphangitis carcinomatosa.
• Allergic reactions to birds, drugs, or family history of similar conditions.
• Miliary tuberculosis, histoplasmosis, radiation pneumonitis.
• Drug-induced lung disease (e.g., Busulphan, Paraquat).

Investigations

• FBC: May show low haemoglobin or polycythaemia.
• Pulmonary Function Tests (PFTs): Show a progressive restrictive defect with reduced lung volumes and DLco (diffusing capacity for carbon monoxide).
• ABG: Often shows low PaO₂ (Type 1 respiratory failure), especially during exercise.
• Rheumatoid Factor/ANA: Positive in up to 30% of cases.
• CXR: Bilateral basal reticulonodular shadowing with progressive fibrosis.
• HRCT: Differentiates between UIP (honeycomb pattern, poor steroid response) and DIP (ground-glass appearance, better steroid response).
• Lung Biopsy: Considered in select cases but carries risks of complications.

Complications

• Progressive respiratory failure (Type 1).
• Development of pulmonary hypertension and cor pulmonale.
• Increased susceptibility to chest infections.
• Increased risk of lung cancer.
• Ultimately, death is often due to respiratory failure.

Prognostic Indicators

• Better prognosis in younger females with a good response to steroids.
• HRCT showing a ground-glass appearance rather than honeycomb changes.
• DIP histology suggests a better response to therapy than UIP.

Management

• Antifibrotic Agents: Pirfenidone and Nintedanib for those with a vital capacity between 50-80% predicted.
• Lifestyle: Smoking cessation and graded exercise as tolerated.
• Symptom Control: Treat gastroesophageal reflux to reduce cough and pulmonary symptoms.
• Vaccinations: Ensure up-to-date influenza and pneumococcal vaccination.
• Antibiotics: Early intervention for infective episodes.
• Lung Transplantation: Considered for select cases; single lung transplant is possible but carries risks of malignancy.
• Palliation: Median survival is approximately 2.8 years; home oxygen and supportive care are crucial for advanced stages.