Restrictive Pulmonary Diseases

Restrictive Pulmonary Diseases

Restrictive Pulmonary Diseases

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RLDs Overview - Lungs Under Pressure

RLDs: Group of disorders causing ↓ lung expansion & ↓ Total Lung Capacity (TLC).

  • Pathophysiology: ↑ Lung stiffness (↓ compliance) or chest wall/neuromuscular dysfunction.
  • Key PFTs:
    • Hallmark: ↓ TLC (<80% predicted)
    • ↓ FVC, ↓ FEV1
    • FEV1/FVC ratio: Normal or ↑ (typically >0.7 as both ↓ proportionally or FVC ↓ more)
    • ↓ DLCO (common in parenchymal RLDs)
  • Types:
    • Intrinsic (Parenchymal): IPF, Sarcoidosis
    • Extrinsic: Kyphoscoliosis, Myasthenia Gravis

PFT spirometry graphs: Normal, Obstruction, Restriction

⭐ Hallmark of RLDs is a decreased Total Lung Capacity (TLC) with a normal or increased FEV1/FVC ratio.

IIPs Deep Dive - Mysterious Fibrosis

Idiopathic Interstitial Pneumonias (IIPs): Group of diffuse parenchymal lung diseases of unknown cause, characterized by varying degrees of inflammation and fibrosis. Focus on IPF.

  • Idiopathic Pulmonary Fibrosis (IPF): Most common and severe IIP.
    • Etiology: Unknown; associations: smoking, genetics (e.g., MUC5B, TERT, TERC).
    • Pathology: Usual Interstitial Pneumonia (UIP) pattern is the hallmark.
      • Key features: Temporal heterogeneity (old & new fibrosis), spatial heterogeneity (patchy), fibroblastic foci (active fibrosis), architectural distortion.
      • Gross/CT: Honeycomb lung (esp. subpleural, basal).
    • Clinical: Insidious onset dyspnea, dry cough, digital clubbing, bibasilar inspiratory crackles ("velcro rales").
    • Diagnosis: HRCT (typical UIP: subpleural, basal predominant reticulation, honeycombing, traction bronchiectasis). Biopsy if HRCT atypical.
    • Prognosis: Poor, median survival ~3-5 years post-diagnosis.

    Fibroblastic foci are crucial microscopic findings in UIP, representing sites of ongoing, active collagen deposition by myofibroblasts.

  • Other notable IIPs:
    • Non-Specific Interstitial Pneumonia (NSIP): Better prognosis than IPF; cellular or fibrotic patterns.
    • Cryptogenic Organizing Pneumonia (COP): Good response to steroids.

HRCT chest showing typical UIP pattern in IPF

Occupational & Environmental RLDs - Inhaled Insults

  • Pneumoconioses: Inorganic dust inhalation → macrophage activation → fibrosis.
    • Coal Worker's Pneumoconiosis (CWP): Coal dust. Simple (macules/nodules <1cm, upper lobes); Complicated (Progressive Massive Fibrosis, PMF >2cm). Caplan Syndrome (CWP + RA nodules).

    • Silicosis: Silica dust (mining, sandblasting). ↑ TB risk (impaired macrophage function). Eggshell calcification of hilar lymph nodes. Apical fibronodules.

    • Asbestosis: Asbestos fibers. Ferruginous bodies. Pleural plaques (most common manifestation, parietal). Basilar predominant fibrosis. ↑ Risk: Bronchogenic carcinoma (most common cancer), mesothelioma.

    • Berylliosis: Beryllium exposure. Non-caseating granulomas; mimics sarcoidosis.

  • Hypersensitivity Pneumonitis (HP): Immune-mediated (Type III/IV hypersensitivity) response to inhaled organic antigens.
    • Examples: Farmer's lung (Saccharopolyspora rectivirgula), Bird fancier's lung (avian proteins).
    • Acute: Fever, cough, dyspnea 4-8 hrs post-exposure; reversible. Chronic: Insidious onset, progressive dyspnea, irreversible fibrosis; non-caseating granulomas.

⭐ In asbestosis, bronchogenic carcinoma is a more common malignancy than mesothelioma, especially with co-existing smoking (synergistic effect).

Systemic & Other RLDs - Wider Connections

  • Connective Tissue Diseases (CTDs) causing RLD:
    • Systemic Sclerosis (Scleroderma): Most common CTD to cause ILD (NSIP pattern common).
    • Rheumatoid Arthritis (RA): Usual Interstitial Pneumonia (UIP) pattern common; Caplan syndrome (RA + pneumoconiosis).
    • Systemic Lupus Erythematosus (SLE): Pleuritis, pleural effusions, acute lupus pneumonitis, diffuse alveolar hemorrhage, shrinking lung syndrome.
    • Polymyositis/Dermatomyositis: NSIP, organizing pneumonia.
    • Sjögren's Syndrome: Lymphocytic interstitial pneumonia (LIP).
  • Drug-Induced RLDs:
    • Amiodarone: Pneumonitis, fibrosis.
    • Bleomycin: Dose-dependent pneumonitis, fibrosis.
    • Methotrexate: Hypersensitivity pneumonitis.
    • Nitrofurantoin: Acute pneumonitis, chronic fibrosis.
    • 📌 Mnemonic: "Bad Air Makes No Lungs Happy" (Bleomycin, Amiodarone, Methotrexate, Nitrofurantoin, Lomustine (CCNU), Heroin)
  • Radiation-Induced Lung Disease:
    • Radiation Pneumonitis: Acute (1-6 months post-radiation); lymphocytic alveolitis.
    • Radiation Fibrosis: Chronic (>6-12 months post-radiation); dense fibrosis.

CT scans of drug-induced interstitial lung disease patterns

⭐ Amiodarone lung toxicity classically shows foamy macrophages on BAL or biopsy due to phospholipidosis, and high-attenuation areas on CT scan due to iodine content.

  • Other Causes:
    • Neurofibromatosis
    • Tuberous Sclerosis (LAM - Lymphangioleiomyomatosis)
    • Graft-versus-Host Disease (GVHD) post-transplant (Bronchiolitis Obliterans).

High‑Yield Points - ⚡ Biggest Takeaways

  • Restrictive diseases: ↓ lung volumes (↓TLC, ↓FVC), normal/↑ FEV1/FVC ratio.
  • IPF: Usual Interstitial Pneumonia (UIP) pattern, honeycomb lung on HRCT.
  • Sarcoidosis: Non-caseating granulomas, bilateral hilar lymphadenopathy, ↑ACE.
  • Pneumoconioses: Caused by inorganic dust inhalation (e.g., silica, asbestos), leading to fibrosis.
  • Asbestosis: Associated with pleural plaques, ↑ risk of mesothelioma and bronchogenic carcinoma.
  • Hypersensitivity Pneumonitis: Immune reaction to inhaled organic antigens (e.g., farmer's lung).
  • ARDS: Characterized by Diffuse Alveolar Damage (DAD) and hyaline membrane formation.

Practice Questions: Restrictive Pulmonary Diseases

Test your understanding with these related questions

Which one of the following conditions is not associated with rheumatoid arthritis? (If all are associated, select 'None').

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Flashcards: Restrictive Pulmonary Diseases

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Which subtypes of idiopathic interstitial pneumonia are associated with smoking?_____

TAP TO REVEAL ANSWER

Which subtypes of idiopathic interstitial pneumonia are associated with smoking?_____

Respiratory bronchiolitis associated ILD (RB-ILD) and Desquamative interstitial pneumonia (DIP)

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