1. (Idiopathic) Pulmonary Fibrosis

1.1 Epidemiology

• Definition
  • Interstitial lung disease (ILD), also known as diffuse parenchymal lung disease (DPLD), represents a group of non-infective conditions involving infiltration of the lung interstitium and alveoli.
• Prevalence
  • ILD affects approximately 80 per 100,000 men and 70 per 100,000 women globally.
  • Pulmonary fibrosis and sarcoidosis together comprise the majority of ILDs.
• Pulmonary Fibrosis
  • The incidence of idiopathic pulmonary fibrosis (IPF) is ~5 per 100,000 person-years. An estimated 2000new cases occur yearly in the UK.
  • Worldwide, IPF incidence ranges 14–43 per 100,000.
  • More common in men and in smokers.
  • Median age at presentation is around 70 years.

1.2 Aetiology

• Restrictive Disease Overview
  • Restrictive lung diseases reduce lung volumes (↓TLC, ↓FVC), typically causing increased FEV₁:FVC ratio because both FEV₁ and FVC decrease but FVC falls more.
• Pulmonary Fibrosis
  • An end result of various pathologies that lead to alveolar epithelial damage with excessive fibrosis and scarring.
  • Idiopathic Pulmonary Fibrosis (IPF): Accounts for ~60% of ILD. Historically known as cryptogenic fibrosing alveolitis.
  • Connective Tissue Diseases: (10–20% of ILD). Commonly associated with rheumatoid arthritis, systemic sclerosis, dermatomyositis.
  • Drug-Induced: e.g. chemotherapy agents (bleomycin, methotrexate) or other drugs like amiodarone, etc.
  • Radiotherapy-Related: 5–15% of patients may develop radiotherapy-induced pneumonitis that can evolve into fibrosis.
  • Other: Hypersensitivity pneumonitis, sarcoidosis, pneumoconiosis, chronic aspiration, acute respiratory distress syndrome (ARDS).

1.3 Risk Factors

• Age: IPF typically in older adults (median age ~70).
• Smoking: Strongly associated with IPF.
• Occupational Exposures: Dust, fumes.
• Chemotherapy/Radiotherapy: Pulmonary toxicity.
• Connective Tissue Diseases: e.g. rheumatoid arthritis, systemic sclerosis.

1.4 Symptoms

• Progressive Breathlessness (over months to years)
  • Occasional acute or subacute onset if drug- or radiotherapy-induced.
• Dry Cough
  • Typically persistent and non-productive.
• Signs on Examination:
  • Finger clubbing (~15–25% of cases).
  • Reduced bilateral chest expansion.
  • Fine late-inspiratory ‘Velcro’ crackles (often bibasally).
  • Possible cyanosis and cor pulmonale features (if severe).
  • Coexisting signs of connective tissue disease (e.g. swollen joints in rheumatoid arthritis).

1.5 Diagnosis

1.5.1 Investigations

1. Pulmonary Function Tests (PFTs)
   • Restrictive Defect: ↓Total Lung Capacity, ↓FVC, normal or increased FEV₁:FVC ratio.
   • Reduced Transfer Factor (TLCO <40% indicates severe disease).
   • 6-min walk test can assess functional impairment.
2. Chest X-Ray
   • May show diffuse basal reticular (reticulonodular) opacities.
   • Often insensitive or non-specific, used to exclude other pathologies (infection, tumour).
3. High-Resolution CT (HRCT)
   • Essential to identifying the pattern of fibrosis:
     • Usual Interstitial Pneumonia (UIP): Subpleural, basal honeycombing, heterogenous lesions.
     • Non-Specific Interstitial Pneumonia (NSIP): Ground-glass opacities, more uniform.
   • Radiotherapy-induced fibrosis localises to the irradiated field with a straight boundary.
4. Blood Tests
   • Rheumatoid factor, antinuclear antibodies, creatine kinase, etc., to detect underlying connective tissue disease.
   • Specific precipitins if hypersensitivity pneumonitis suspected.
   • Serum ACE if sarcoidosis is a possibility.
5. Bronchoscopy and Bronchoalveolar Lavage
   • Excludes alternative diagnoses (infection, sarcoidosis, hypersensitivity pneumonitis).
6. Lung Biopsy (Surgical)
   • Required only if diagnosis remains uncertain or if management hinges on histological confirmation.

1.5.2 Diagnostic Criteria for IPF

• Joint American Thoracic Society–European Respiratory Society guidelines specify:
  • Major Criteria: Exclusion of other causes (drugs, exposures, connective tissue disease), presence of restrictive PFT pattern with impaired gas exchange, bibasilar reticular changes on HRCT, and non-diagnostic bronchoalveolar lavage or transbronchial biopsy.
  • Minor Criteria: Age >50 years, insidious onset (>3 months) of dyspnoea, bibasilar ‘Velcro’ crackles, progressive course.

1.6 Immediate Management

• Acute Deteriorations
  • Identify possible triggers (infection, drug-induced, acute radiation pneumonitis).
  • High-dose corticosteroids sometimes used if significant inflammatory component is suspected.
  • Supportive care: oxygen therapy if hypoxaemic, cautious fluid management to avoid overload.

1.7 Long-Term Management

• Remove/Address Underlying Causes
  • Discontinue offending drugs or reduce radiation exposure if feasible.
  • Aggressive management of gastro-oesophageal reflux or chronic aspiration if present.
• Pharmacotherapy
  • High-dose systemic corticosteroids (0.5–1 mg/kg) or immunosuppressants (azathioprine, cyclophosphamide) in certain subtypes (e.g. NSIP, connective tissue disease–related).
  • Pirfenidone or nintedanib can slow disease progression in idiopathic pulmonary fibrosis.
  • N-acetylcysteine sometimes used but evidence is limited.
• Supportive Measures
  • Pulmonary rehabilitation.
  • Long-term oxygen therapy for severe resting hypoxaemia.
  • Manage comorbidities (e.g. cor pulmonale).
• Lung Transplantation
  • Consider in patients <65 years old with progressive disease (≥10% decrease in FVC or ≥15% drop in TLCO over 6 months) and no contraindications.
• Prognosis
  • Idiopathic Pulmonary Fibrosis: 5-year survival of ~10–15%. Usually progressive and aggressive.
  • Fibrosis with connective tissue disease: Better overall prognosis.
  • Drug-/Radiation-induced: May show initial rapid decline or partial stabilisation once exposure ends.

2. Hypersensitivity Pneumonitis

2.1 Epidemiology

• Definition
  • Hypersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, is an interstitial lung disease caused by an immunological (type IV hypersensitivity) reaction to inhaled organic antigens.
• Prevalence
  • In the UK, bird fancier’s lung is the most common form, while farmer’s lung affects 0.4–7% of farm workers.
• Smoking
  • Curiously, smoking reduces the risk of hypersensitivity pneumonitis, which is an exception among respiratory disorders.

2.2 Aetiology

• Mechanism
  • Repeated or ongoing inhalation of organic or environmental antigens triggers a delayed-type (cell-mediated) immune response in the small airways and alveoli.
  • This leads to granulomatous inflammation and can progress to pulmonary fibrosis, especially in the upper lobes.
• Common Antigen Exposures
  • Bird Fancier’s Lung: Avian proteins (feathers, droppings, serum).
  • Farmer’s Lung: Thermophilic actinomycetes in mouldy hay.
  • Mushroom Worker’s Lung: Thermophilic actinomycetes, mushroom spores.
  • Malt Worker’s Lung: Aspergillus clavatus in barley.
  • Winemaker’s Lung: Botrytis cinerea on grapes.
  • Hot Tub Lung: Aerosolised Mycobacterium avium from heated water.

2.3 Risk Factors

• Occupational or Hobby-Related
  • Bird keepers (pigeons, exotic pet birds).
  • Farming (exposure to hay, straw).
  • Mushroom cultivation, malt spreading, winemaking, hot tub use.
• Repeated High-Level Exposure
  • Chronic or frequent contact with the antigens in question.
• Non-Smoking Status
  • Non-smokers paradoxically have a higher risk of HP relative to smokers.

2.4 Symptoms

• Acute Hypersensitivity Pneumonitis
  • Episodes of breathlessness, wheeze, cough, fever, and crepitations typically begin 4–6 hours after antigen exposure.
  • Symptoms usually resolve within 48–72 hours once the exposure is removed.
• Chronic Hypersensitivity Pneumonitis
  • Gradual onset of progressive dyspnoea and a dry cough, mimicking pulmonary fibrosis.
  • Additional systemic symptoms: fatigue and weight loss.
  • Some patients do not have a clear history of acute episodes.

2.5 Diagnosis

2.5.1 Clinical Assessment

• History of Exposure
  • Identification of a specific antigen source is essential (e.g. birds, mouldy hay, contaminated water).
• Pulmonary Function Tests
  • Often a restrictive pattern or mixed restrictive–obstructive defect.
  • Reduced transfer factor (TLCO).
• Specific Immunological Sensitisation
  • Blood tests for specific IgG antibodies (e.g. avian precipitins).
  • A positive test indicates exposure, but not necessarily active disease.
• Imaging
  • Chest X-Ray:
    • Patchy diffuse infiltrates in acute presentations.
    • Reticulonodular shadowing in chronic disease.
    • Upper and middle zone predominance is common (in contrast to usual pulmonary fibrosis).
  • High-Resolution CT: Ground glass consolidation, centrilobular nodules, mosaic attenuation, fibrotic changes (in advanced disease).
• Bronchoscopy
  • Bronchoalveolar lavage fluid typically shows >40% lymphocytosis.
• Lung Biopsy
  • Transbronchial or surgical biopsies may reveal small, poorly formed non-caseating granulomas, mononuclear cell infiltrates, and peribronchial fibrosis.

2.6 Immediate Management

• Remove the Offending Antigen
  • This is critical: rehoming birds, discarding mouldy hay, or rectifying contaminated water sources.
• High-Dose Systemic Corticosteroids (0.5–1 mg/kg)
  • May benefit some patients, though effectiveness is inconsistent.
• Prognosis
  • Acute episodes may fully resolve once exposure ceases.
  • Chronic disease emerges from repeated attacks, potentially leading to end-stage pulmonary fibrosis if exposure is not avoided.

2.7 Long-Term Management

• Strict Antigen Avoidance
  • The single most effective measure to stop disease progression.
• Supportive Therapies
  • Monitoring lung function for signs of progression to fibrosis.
  • Treating complications like respiratory failure if it arises.
• Outcome
  • Prognosis depends heavily on whether ongoing exposure can be eliminated. Chronic hypersensitivity pneumonitis can cause permanent scarring and functional loss.

3. Pneumoconioses

3.1 Epidemiology

• Definition
  • Pneumoconiosis refers to lung damage caused by inhalation of mineral dusts over a prolonged period, typically in an occupational setting.
• Prevalence and Recognition
  • The disease usually develops insidiously over years of exposure.
  • In the UK, patients with pneumoconiosis and impaired lung function are entitled to compensation.

3.2 Aetiology

• Chronic Inhalation of Fibrogenic Dusts
  • Repeated or severe exposure to specific mineral dusts triggers lung injury and fibrotic remodelling.
  • Examples of dusts include asbestos, coal, silica, beryllium, and others.
• Pathophysiological Mechanism
  • Alveolar macrophages engulf the inhaled particles and release cytokines → persistent inflammation → progressive pulmonary fibrosis.

3.3 Risk Factors

• Occupational Exposures
  • Mining (coal, silica, beryllium).
  • Shipyard work, construction, insulation (asbestos).
  • Sandblasting, stonemasonry (silica).
  • Aerospace industry (beryllium).
• Duration and Intensity of Exposure
  • Prolonged, high‐level exposure is typically required for significant disease to manifest.

3.4 Symptoms

• General Presentation
  • Progressive breathlessness on exertion, often minimal symptoms initially.
  • Chronic cough, which may be productive (coal worker’s “black sputum”) or mostly non-productive in other pneumoconioses.
• Late Complications
  • Respiratory failure and cor pulmonale.
  • Increased susceptibility to infections (e.g. tuberculosis in silicosis).

3.5 Diagnosis

1. Occupational History
   • Key to suspecting the disease; inquire about past or current jobs with known dust exposure.
2. Imaging
   • Chest X‐ray or CT scan:
     • Asbestosis: Basal fibrosis ± pleural plaques.
     • Coal Worker’s: Multiple small opacities (simple disease) or large fibrotic masses (complicated disease).
     • Silicosis: Nodular opacities in upper lobes, “eggshell” lymph node calcification.
     • Berylliosis: Non‐caseating granulomas, can mimic sarcoidosis.
3. Spirometry
   • Often restrictive pattern (↓TLC, ↓FVC, normal or ↑FEV₁:FVC ratio).
   • May be mixed obstructive–restrictive in advanced disease (e.g. complicated coal workers’ pneumoconiosis).
4. No Specific Biomarkers
   • The diagnosis relies heavily on exposure history and characteristic radiographic findings.

3.6 Immediate Management

• Removal from Further Exposure
  • Stopping inhalation of dusts is the single most important step to limit progression.
• Symptomatic Treatment
  • Bronchodilators if wheezing, oxygen if hypoxaemic.
• Acute Exacerbations
  • Rare in pneumoconioses, but treat infections aggressively and manage complications such as cor pulmonale.

3.7 Long‐Term Management

• No Specific Curative Therapy
  • Supportive care to manage breathlessness and prevent complications.
• Monitoring
  • Serial lung function tests and imaging to detect progressive massive fibrosis or other complications (e.g. necrotic cavitation in silicosis).
• Complication Management
  • Cor pulmonale: treat right heart failure symptoms.
  • Malignancy Surveillance: especially for asbestos-exposed individuals (risk of bronchial carcinoma, mesothelioma).
  • Pneumococcal and influenza vaccinations to reduce infection risk.
• Prognosis
  • Depends on the dust type and level of exposure.
  • Some, like complicated coal worker’s pneumoconiosis and severe silicosis, can be severely debilitating with progressive massive fibrosis.

4. Sarcoidosis

4.1 Epidemiology

• Definition
  • Sarcoidosis is an inflammatory disorder of unknown cause, characterised by non‐caseating granulomasinfiltrating the lung and potentially multiple extra‐pulmonary organs.
• Incidence
  • About 5–10 per 100,000 in the UK, higher in Irish, West Indian, and African‐American populations.
• Demographics
  • Most common age of presentation: 20–40 years.
  • Slightly more common in women than in men.

4.2 Aetiology

• Unknown Cause
  • Possible environmental, viral, or bacterial triggers.
  • Genetic predisposition associated with the HLA‐DRB1*0301 allele.
• Pathogenesis
  • A cell‐mediated immune response leads to non‐caseating granulomas and potentially fibrosis in affected tissues.

4.3 Risk Factors

• Genetic Susceptibility: e.g. association with certain HLA alleles.
• Ethnicity: Higher prevalence in African‐American and West Indian backgrounds.
• Age: Typically young to middle‐aged adults.

4.4 Symptoms

• Pulmonary Involvement (>90% of cases)
  • Dry cough
  • Dyspnoea (progressive)
  • Bilateral hilar lymphadenopathy (often discovered incidentally)
  • Possible fibrotic changes on imaging (leading to traction bronchiectasis)
• Systemic Features (~80%)
  • Low‐grade fever, weight loss, night sweats, decreased appetite
• Organ‐Specific Manifestations
  • Liver: Hepatomegaly, abnormal LFTs in ~60% (rarely cirrhosis/portal hypertension)
  • Spleen and Blood: Splenomegaly; cytopenias (anaemia, lymphopenia)
  • Musculoskeletal: Arthralgias, joint swelling (particularly ankles, knees, wrists, elbows)
  • Kidneys: Hypercalcaemia, nephrolithiasis, renal sarcoidosis
  • Eyes (25%): Uveitis, scleritis, optic atrophy (rare)
  • Skin (25%): Erythema nodosum (acute disease), lupus pernio (chronic disease)
  • Heart (5–25%): Conduction defects, arrhythmias, restrictive cardiomyopathy
  • CNS (5–20%): Cranial nerve palsies, optic neuritis, peripheral neuropathy
  • Salivary Glands (5%): Parotid enlargement, possible Heerfordt’s syndrome (with facial palsy)
  • Endocrine (5%): Hypercalcaemia, pituitary involvement → rare hypopituitarism
  • ENT: Nasal or sinus granulomas, rarely destructive lesions

Clinical Patterns

• Acute Sarcoidosis (Löfgren’s Syndrome)
  • Bilateral hilar lymphadenopathy, erythema nodosum, low‐grade fever, arthralgias.
• Chronic Sarcoidosis
  • Insidious onset, relapsing–remitting course, progressive in ~30%.
  • Pulmonary fibrosis may ensue in advanced disease.

4.5 Diagnosis

4.5.1 Clinical Assessment

• Pulmonary: Dry cough, progressive dyspnoea, bilateral hilar lymphadenopathy often detected on routine chest X‐ray.
• Extra‐Pulmonary: Multi‐system involvement (see table above).

4.5.2 Investigations

1. Blood Tests
   • Serum ACE elevated in up to 80%, often mirroring disease activity.
   • Hypercalcaemia in 2–5%.
   • LFT abnormalities with liver involvement.
2. Pulmonary Function Tests
   • Mixed obstructive–restrictive pattern or purely restrictive.
   • Reduced transfer factor (TLCO).
3. Imaging
   • Chest X‐ray: Four stages:
     • Stage 0: Normal.
     • Stage 1: Bilateral hilar lymphadenopathy.
     • Stage 2: Bilateral hilar lymphadenopathy + parenchymal infiltrates.
     • Stage 3: Parenchymal infiltrates only.
     • Stage 4: Advanced fibrosis.
   • High‐resolution CT: Shows nodular infiltrates, fibrotic changes, and alveolar involvement if present.
4. Tissue Biopsy
   • Histological confirmation of non‐caseating granulomas is required to secure the diagnosis.
   • Other granulomatous conditions (TB, fungal infections, hypersensitivity pneumonitis) must be excluded.
5. Other
   • ECG or 24‐hour Holter: Checks for arrhythmias or heart block.
   • MRI/Echo: Detects potential involvement of brain or heart.

4.6 Immediate Management

• Many Cases: Asymptomatic or mildly symptomatic → no immediate therapy needed.
• Organ-Threatening Involvement (eyes, heart, nervous system, kidneys) or severe pulmonary disease →
  • Systemic Corticosteroids to reduce granulomatous inflammation.
  • If unresponsive or severe, second‐line agents (hydroxychloroquine, methotrexate, infliximab) may be considered.

4.7 Long-Term Management

1. Monitoring
   • Regular assessment of lung function, imaging, and organ involvement (e.g. eyes, kidneys, heart).
   • Serum ACE levels may help track disease activity (though not always reliable).
2. Pharmacotherapy
   • Prolonged corticosteroids for persistent or severe involvement.
   • Alternative immunosuppressants if steroids alone are insufficient or cause intolerable adverse effects.
3. Prognosis
   • Acute Sarcoidosis (Löfgren’s syndrome) typically resolves within ~2 years.
   • Chronic Sarcoidosis: 30% develop progressive disease; 5–10% may die from complications (respiratory failure, arrhythmias).
   • Poor prognostic factors include older age at presentation, African or Caribbean ethnicity, and advanced pulmonary fibrosis.

5. Rare Types of ILD and Lung Infiltrations

5.1 Epidemiology

• Definition
  • A group of uncommon or atypical interstitial lung diseases with distinct causes, presentations, and CT appearances.
• Representative Conditions
  • Eosinophilic and organising pneumonias
  • Lymphocytic interstitial pneumonia (LIP)
  • Lymphangiomyomatosis
  • Langerhans cell histiocytosis (LCH)
  • Alveolar proteinosis
  • Amyloidosis
  • Lymphangitis carcinomatosis

These conditions each have characteristic clinical, radiological, or histological findings and can lead to restrictive lung function and progressive breathlessness.

5.2 Aetiology

5.2.1 Eosinophilic and Organising Pneumonias

• Pathology
  • Eosinophilic pneumonia: alveolar infiltrates with eosinophils.
  • Organising pneumonia: intraluminal plugs of connective tissue in alveolar ducts and alveoli.
• Causes
  • Usually idiopathic.
  • Eosinophilic pneumonia also triggered by drugs or parasite infestation (e.g. Toxocara, Ascaris → Löffler’s syndrome).
  • Organising pneumonia can be associated with connective tissue diseases, drugs (amiodarone), radiotherapy, or infections.

5.2.2 Lymphocytic Interstitial Pneumonia (LIP)

• Pathology: Interstitial infiltration with lymphocytes.
• Aetiology: Usually idiopathic, or associated with HIV or autoimmune diseases.

5.2.3 Lymphangiomyomatosis and Langerhans Cell Histiocytosis (LCH)

• Shared Feature: Both produce lung cysts visible on imaging.
• Lymphangiomyomatosis: Smooth muscle proliferation → cystic change, primarily in women; associated with tuberous sclerosis.
• Langerhans Cell Histiocytosis: Infiltration by dendritic (Langerhans) cells; almost exclusively in smokers.

5.2.4 Alveolar Proteinosis

• Pathology: Lipoproteinaceous material accumulates in alveoli.
• Aetiology: Usually idiopathic; rarely secondary to impaired alveolar macrophage function.

5.2.5 Amyloidosis

• Pathology: Deposition of amyloid proteins in lungs, forming diffuse or nodular infiltrates; can also cause endobronchial lesions.

5.2.6 Lymphangitis Carcinomatosis

• Pathology: Malignant infiltration of pulmonary lymphatics by lung cancer or metastatic cells → progressive dyspnoea, restrictive lung pattern.

5.3 Risk Factors

1. Eosinophilic and Organising Pneumonias
   • Potential drug exposures (e.g. amiodarone).
   • Parasitic infections in eosinophilic pneumonia.
   • Underlying rheumatological conditions for organising pneumonia.
2. Lymphocytic Interstitial Pneumonia
   • HIV infection or certain autoimmune disorders.
3. Lymphangiomyomatosis
   • Occurs only in women, often with tuberous sclerosis.
4. Langerhans Cell Histiocytosis
   • Smoking is almost always present.
5. Alveolar Proteinosis
   • Usually idiopathic; less commonly immune defects impair alveolar macrophage function.
6. Amyloidosis
   • May be secondary to chronic inflammatory conditions or plasma cell dyscrasias.
7. Lymphangitis Carcinomatosis
   • Advanced or metastatic malignancy.

5.4 Symptoms

1. Eosinophilic / Organising Pneumonias
   • Short history of dry cough, dyspnoea, fever.
   • Eosinophilic pneumonia can cause marked peripheral eosinophilia and fleeting pulmonary opacities.
2. Lymphocytic Interstitial Pneumonia
   • Progressive breathlessness, cough.
   • May present with features of HIV or rheumatological disease.
3. Lymphangiomyomatosis and LCH
   • Both cause progressive respiratory failure due to cyst formation.
   • Lymphangiomyomatosis: can lead to spontaneous pneumothoraces, chylous effusions.
   • LCH: can cause cystic changes and increased risk of pneumothorax in smokers.
4. Alveolar Proteinosis
   • Cough, dyspnoea, alveolar opacities on imaging.
5. Amyloidosis
   • May show diffuse or nodular lung infiltrations, or endobronchial lesions; can lead to breathlessness and cough.
6. Lymphangitis Carcinomatosis
   • Progressive dyspnoea with minimal chest signs; often overshadowed by the features of underlying malignancy.

5.5 Diagnosis

1. Imaging
   • CT is often critical in identifying characteristic patterns (e.g. cystic changes in LAM/LCH, alveolar infiltrates in alveolar proteinosis).
2. Bronchoscopy / Bronchoalveolar Lavage
   • >25% eosinophils in eosinophilic pneumonia.
   • Lymphocytic interstitial pneumonia has lymphocytic infiltration.
   • Alveolar proteinosis diagnosed by presence of milky, lipoproteinaceous fluid in alveolar lavage.
3. Histology (biopsy)
   • Non-caseating granulomas or plugs of connective tissue in organising pneumonia.
   • Amyloid deposits on Congo red staining for amyloidosis.
   • Smooth muscle proliferation (lymphangiomyomatosis); infiltration by Langerhans cells in LCH.

5.6 Immediate Management

1. Eosinophilic / Organising Pneumonias
   • Rapid response to systemic corticosteroids.
   • Identify and discontinue any offending drugs or treat parasitic infection.
2. Lymphocytic Interstitial Pneumonia
   • Corticosteroids; address underlying HIV or autoimmune disease.
3. Lymphangiomyomatosis
   • May require hormonal modulation (e.g. medroxyprogesterone), calcineurin inhibitors (tacrolimus).
   • Manage pneumothoraces or chylous effusions if they occur.
4. Langerhans Cell Histiocytosis
   • Smoking cessation is crucial and can stabilise or improve lung function.
   • No other specific therapy proven effective.
5. Alveolar Proteinosis
   • Whole-lung lavage or granulocyte–macrophage colony-stimulating factor (GM-CSF) injections.
6. Amyloidosis
   • No direct therapy for lung infiltration; treat underlying condition if secondary.
   • Supportive care for respiratory compromise.
7. Lymphangitis Carcinomatosis
   • Usually indicates advanced malignancy with poor prognosis; no specific treatment beyond palliation.

5.7 Long-Term Management

• Monitoring:
  • Serial lung function testing and imaging to observe progression.
• Prevention of Exposure:
  • If a triggering antigen or agent is implicated (e.g. certain drugs, toxins).
• Treat Underlying Disease:
  • Address parasitic infections, immunodeficiencies, or autoimmune disorders as appropriate.
• Prognosis:
  • Varies widely by condition. Some (e.g. organising pneumonia, eosinophilic pneumonia) respond well to steroids, while others (e.g. lymphangitis carcinomatosis) often have a grave outlook.