Interstitial lung diseases (ILDs) 

affect the lung interstitium, i.e. the space between the alveolar epithelium and the capillary endothelium, causing inflammation and fibrosis.

ILD refers to over 200+ disease entities which share a common pathological process. The interstitium is damaged, leading to progressive pulmonary fibrosis

Aetiology

• Idiopathic interstitial pneumonia:
  • Idiopathic pulmonary fibrosis
  • Other idiopathic causes
• Connective tissue diseases (eg RA, SLE)
• Sarcoidosis
• Pneumoconioses (eg asbestos, coal, silicon etc)
• Hypersensitivity pneumonitis (eg bird dander, fungal spores etc)
• Drugs (eg amiodarone)

main types:

• pulmonary fibrosis
  • tends to occur in older adults
  • causes significant morbidity and mortality
  • Idiopathic pulmonary fibrosis
    • relatively rare, progressive, chronic pulmonary fibrosis of unknown aetiology
    • It typically occurs in patients 45-65 years, male predominance, and a history of smoking is frequently found
    • involves the lower lobes
    • HRCT: characteristic ‘usual interstitial pneumonia’ (UIP) pattern. basal, sub-pleural reticular abnormalities, and honeycombing and traction bronchiectasis
    • Poor prognosis – median survival 3-5 years. Typically older adults
• sarcoidosis
  • a multi-system disease that results in pulmonary fibrosis in up to 20% of patients
  • tends to occur in younger adults
  • has a more benign prognosis and in many cases, resolves by itself
• occupational lung diseases (pneumoconiosis)
  • Variable prognosis depending on the cause
• Drugs related
  • Cyclophosphamide
  • Methotrexate
  • amiodarone
• Hypersensitivity ILD
  • Usually has a good prognosis if the allergen is avoidednterstitial lung disease secondary to connective tissue diseases.

Causes of pulmonary fibrosis can be divided into those that affect the upper lobes and those predominantly affecting the lower lobes

Causes

Upper lobes (SCHART-S)

• silicosis (progressive massive fibrosis), sarcoidosis
• coal workers’ pneumoconiosis (progressive massive fibrosis)
• histiocytosis
• ankylosing spondylitis
• allergic bronchopulmonary aspergillosis
• radiation
• tuberculosis

Lower lobes (RASCO)

• rheumatoid arthritis
• asbestosis
• scleroderma
• cryptogenic fibrosing alveolitis
• other (drugs, e.g. busulphan, bleomycin, nitrofurantoin, hydralazine, methotrexate, amiodarone)

Presentation

• Suspect if patient presents with progressively worsening dyspnoea (especially on exertion), non-productive cough.
• Suspect if patient has new pulmonary symptoms in the context of a known connective tissue disease.

• Often slowly progressive
• Occasionally may mimic an acute pneumonia
• Dry cough
• Progressive shortness of breath
• May have clubbing
• May have diffuse inspiratory crackles
• Wheeze, haemoptysis and chest pain are rare

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Investigations

• • Blood
    • FBC (raised ESR)
    • Rh factor (+ve 50% patients)
    • ANA (30% +ve)
  • Pulse oximetry/ arterial blood gas  – Low SpO₂, Low PaO₂
  • full lung function testing
    • spirometry  – Restrictive respiratory pattern – Fev1/FVC ratio >80%
    • lung volumes – reduction in lung volumes
    • diffusing capacity for carbon monoxide (Dlco) – decrease in the Dlco
  • CXR
    • Irregular, reticulo-nodular shadows, often in lower zones, sometimes called the reticulonodular pattern
    • CXR is often normal
  • CT
    • Usually a “high resolution CT” (HRCT) 
    • Ground-glass opacification
    • “Honeycombing”
    • “Mosaicism”
    • 
  • 6-minute walk test
    • Reduced walk distance
    • Oxygen desaturation
  • Broncoscopy
  • Surgical Lung Biopsy

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Management

Idiopathic pulmonary fibrosis: no therapy has been show to have benefit. Medial survival 3-5 years after diagnosis.

Sarcoidosis: treat only if there is progressive disease. Steroids 6-24 months is the norm.

The exact management plan is very individualised for the patient. 

Some, all or none of the below measures may be used. For idiopathic pulmonary fibrosis, no treatment has been proven to prolong survival.

General Measures

• Avoidance of trigger if known: stopping medications, changing jobs etc.
• Stop smoking
  • Smoking cessation is extremely important for any smokers with ILDs
• Pulmonary rehabilitation
  • Early referral to a specialist centre for pulmonary rehabilitation is important
• Oxygen therapy if significant hypoxia
• Treating comorbidities
• Reduce infection
  • Vaccinations
  • Minimise sick contacts 
  • Timely antibiotic therapy

Medications

• Immunosuppression
  • Corticosteroids
  • azathioprine 
  • cyclophosphamide
• Treat associated disorders
  • GORD
    • Proton pump inhibitor
    • H2-receptor antagonist
    • Prokinetic agents (mainly scleroderma)
    • Surgery in selected cases
  • Pulmonary hypertension
    • Supplemental oxygen
    • Diuretics (for right heart failure)
    • Vasodilator therapy in selected cases
  • Depression and anxiety
  • Osteoporosis
    • Vertebral and rib fractures can further restrict breathing, as well as impact on quality of life
    • Vitamin D repletion
    • Surveillance bone mineral densitometry
    • Bisphosphonates
    • Endocrinologist referral in some cases
• Lung transplant
  • should be considered in suitable candidates

Specific Treatments

• Idiopathic pulmonary fibrosis
  • no therapy has been proven to improve the survival or otherwise significantly alter the clinical course of iPF. 
  • there is no evidence to support the widespread use of high dose prednisolone alone, and its use is associated with significant morbidity. 
  • A trial of prednisolone, azathioprine and n-acetyl cysteine may be warranted but strong evidence for benefit is lacking
  • Most patients with Idiopathic pulmonary fibrosis die within 5 years of diagnosis. 
• Most other types of ILD have a better prognosis.

• Sarcoidosis
  •  treatment only indicated if disease is progressive and / or has significant symptoms
  • Prednisolone – 0.5mg/Kg/day is usually the recommended treatment, for one month, and then weaning to the lowest effective dose, reviewed every 6-12 months
• Connective tissues diseases
  • treat the underling disorder. Often a similar prednisolone regimen to that recommended for sarcoidosis
• Hypersensitivity pneumonitis
  • voidance of the antigen is the primary treatment. Prednisolone may be used if there is severe or progressive disease