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Interstitial lung disease (ILD)

Classification The ILDs can be broadly grouped into three categories: (Ref. Hari. 18th ed., Table 261.1 Pg- 2161)

  1. Those with known aetiology eg
    1. Occupational/environmental eg asbestosis, berylliosis, silicosis, cold dust
    2. Drugs eg nitrofurantoin, bleomycin, amiodarone, sulfasalazine, busulfan Q
    3. Hypersensitivity reactions eg extrinsic allergic alveolitis
    4. Infections eg TB, fungi, viral
  2. Those associated with systemic disorders eg
    1. Sarcoidosis                      
    2. Rheumatoid arthritis                    
    3. SLE,
    4. Systemic sclerosis            
    5. Mixed connective tissue disease            
    6. Sjögren’s syndrome
    7. Ulcerative colitis, renal tubular acidosis, autoimmune thyroid disease
  3. Idiopathic
    1. Idiopathic pulmonary fibrosis (IPF)/cryptogenic fibrosing alveolitis
    2. Cryptogenic organizing pneumonia
    3. Lymphocytic interstitial pneumonia

Important Points:        

  1. Tobacco is not a cause of ILDQ
  2. Exposure to cobalt can lead to giant cell interstitial pneumonitis. Q 

Important Points: - Interstitial lung disease (ILD)

  1. This is the generic term used to describe a number of conditions that primarily affect the lung parenchyma in a diffuse manner.
  2. They are characterized by chronic inflammation Q and/or progressive interstitial fibrosis, and share a number of clinical and pathological features.
  3. Clinical features Dyspnoea Q on exertion; non-productive paroxysmal cough Q, abnormal CXR or high resolution CT; restrictive Q pulmonary spirometry with a reduced DLCO Q.
  4. Pathological features:
  5. Fibrosis and remodeling of the interstitium; chronic inflammation; hyperplasia of type II epithelial cells or type II pneumocytes.  

Important Points:

Extrinsic allergic alveolitis (EAA)

  1. In sensitized individuals, inhalation of allergens (fungal spores or avian proteins provokes a hypersensitivity reaction. In the acute phase, the alveoli are infiltrated with acute inflammatory cells. 
  2. With chronic exposure, granuloma formation and obliterative bronchiolitis occur. There is involvement of type 3 hypersensitivity, (not type 1).
  3. Causes
    1. Bird fancier's Q and pigeon fancier's lung (proteins in bird droppings).
    2. Farmer's Q and mushroom worker's lung (Micropolyspora faeni, Thermoactinomyces vulgaris).
    3. Malt worker's Q lung (Aspergillus clavatus).
    4. Bagassosis Q (Thermoactinomyces). Occur in sugarcane workers.
    5. Byssinosis = cotton fiber
  4. Clinical features 4-6h post-exposure: Fever, rigors, myalgia, dry cough, dyspnea, crackles (no wheeze).
  5. Chronic: Weight loss, exertional dyspnea, Type I respiratory failure, cor pulmonale.
  6. Tests Acute:
  7. CXR: mid-zone mottling/consolidation.
  8. Lung function tests: reversible restrictive defect Q; reduced gas transfer Q during acute attacks. 

In Chronic exposure:

  1. Blood tests: positive serum precipitins.
  2. CXR: upper-zone fibrosis; honeycomb lung.
  3. Lung function tests: persistent changes as above.
  4. Bronchoalveolar lavage (BAL) fluid shows t lymphocytes and mast cells Management
  5. Treatment:
    1. Acute attack: Remove allergen and give O2 (35-60%), then Oral prednisolone (40mg/24h pO), followed by reducing dose.
    2. Chronic: Avoid exposure to allergens, or wear a face mask or +ve pressure helmet. Long-term steroids often achieve CXR and physiological improvement. 

Idiopathic pulmonary fibrosis

  1. The commonest cause of interstitial lung disease,
  2. Inflammatory cell infiltrate and pulmonary fibrosis of unknown cause (also known as cryptogenic fibrosing alveolitis).
  3. Symptoms Dry cough Q; exertional dyspnoea; malaise; weight; arthralgia.
  4. Signs Cyanosis; finger clubbing Q; fine end-inspiratory crepitations Q.
  5. Complications Type 1 respiratory failure; increased risk of lung cancer Q.
  6. Tests Blood:
    1. ABG (decrease PaO2, Decrease PaCO2)
    2. CRP;
    3. immunoglobulins;
    4. ANA (30% +ve,
    5. rheumatoid factor (10% +ve).
    6. CXR: Lung volume , bilateral lower zone reticulo-nodular shadows; honeycomb lung Q (advanced disease).
    7. CT scan show similar changes to the CXR but is more sensitive and is an essential tool for diagnosis.
  7. Spirometry: Restrictive Q pattern is seen.
  8. BAL (broncho alveolar lavage) may indicate activity of alveolitis:
  9. 99TCm-DTPA scan: may reflect disease activity.
  10. Rarely Lung biopsy may be needed for diagnosis.
  11. Management A large proportion of patients have chronic irreversible disease cell unresponsive to treatment
  12. Drugs used are :
    1. Prednisolone
    2. Cyclophosphamide
    3. Lung transplantation

Guidelines for Referral and Transplantation Idiopathic Pulmonary Fibrosis


(Ref. Hari. 18th ed., Pg- 2190, table 266.1)

  1. Referral
    1. Pathologic or radiographic evidence of UIP regardless of vital capacity
  2. Transplantation
    1. Pathologic or radiographic evidence of UIP and any of the following criteria
    2. DLCO <39%
    3. Decrement in FVC 10% during 6 months of follow-up
    4. Decrease in SpO2 below 88% during a 6-min walk test
    5. Honeycombing on HRCT (fibrosis score >2)

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