FlashPath - Lung - Desquamative Interstitial Pneumonia
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This document discusses desquamative interstitial pneumonia (DIP). DIP is characterized by gradual dyspnea and cough over weeks to months. Radiology shows bilateral, lower lobe ground glass opacities. Microscopy reveals intraluminal accumulation of pigmented macrophages in the alveolar spaces. DIP commonly affects heavy smokers and has a good prognosis with smoking cessation and steroid treatment. Differential diagnoses include other interstitial lung diseases that can show focal DIP-like patterns, such as usual interstitial pneumonia, respiratory bronchiolitis, and hypersensitivity pneumonitis.
FlashPath - Lung - Desquamative Interstitial Pneumonia
- 1. FLASHPATH H A Z E M A L I
- 2. DESQUAMATIVE INTERSTITIAL PNEUMONIA H A Z E M A L I
- 3. CLINICAL DIP is one of the “interstitial lung diseases” that show “mild restrictive pulmonary functions” Obstructive airway disease Restrictive airway disease General features (Reduced lung AIRFLOW) Increase in resistance to airflow due to obstruction at any level (Reduced lung VOLUME) Reduced expansion of lung parenchyma Total lung capacity (TLC) Normal / Increased Reduced Forced Expiratory Volume in one second (FEV1) Markedly reduced Normal / slightly reduced
- 4. CLINICAL • Subacute “gradual” dyspnea and cough – Takes weeks – months • Misnomer – Originally thought to be desquamated pneumocytes • Common in heavy smokers – Can be seen also with pneumoconiosis • Radiology (CT) – Bilateral, lower lobe predominance – Ground glass opacities • Good response to Smoking cessation +/- Steroids (GOOD PROGNOSIS)
- 5. GROSS • No specific gross features • Smoking related gross features – Anthracosis – Emphysema – Dilated bronchi with increased mucus secretions
- 6. MICROSCOPY • Intraluminal accumulation of pigmented macrophages – Pattern: Diffuse – Distribution: filling alveolar spaces – Macrophages: finely granular, golden brown pigments • Called “smokers macrophages”
- 7. MICROSCOPY • Mild interstitial chronic inflammation – Mainly lympho-plasmacytic – Plus/minus lymphoid aggregates – Rare eosinophils may be seen – No granulomas or giant cells • Mild interstitial fibrosis – Diffuse interstitial (not bronchiolo-centric) – Alveolar lining: Prominent type II pneumocytes hyperplasia – No Honeycomb changes – No fibroblastic foci
- 8. MICROSCOPY • Other Smoking-related conditions: – Anthracosis – Emphysema – Chronic Bronchitis – Pulmonary eosinophilic granuloma • “Langerhans cell histiocytosis” – Usual interstitial pneumonia
- 9. SPECIAL STUDIES • Macrophages granules stain positive with Iron stains – How to differentiate it from the hemosiderin laden macrophages ? Hemosiderin Laden Macrophages Smokers Macrophages Granules Coarse Fine Vary in size and shape minimal variation Both are Golden brown Refractile Non-refractile
- 10. DIFFERENTIAL DIAGNOSIS • Usual interstitial pneumonia • Respiratory bronchiolitis • Langerhans cell histiocytosis • Hypersensitivity pneumonitis • Other interstitial pneumonias and processes – Acute interstitial pneumonia (diffuse alveolar damage) – Acute fibrinous and organizng pneumonia – Cryptogenic organizing pneumonia (BOOP) – Lymphocytic interstitial pneumonitis – Nonspecific interstitial pneumonia Note that DIP-like areas also seen around scar, tumor, or infarction.
- 11. DIFFERENTIAL DIAGNOSIS • Usual interstitial pneumonia – Disturbed lung architecture (prominent honeycombing) – Marked interstitial fibrosis – Frequent fibroblastic foci (temporal heterogeneity) – can show focal DIP-like areas • Respiratory bronchiolitis – Bronchiolo-centric – Patchy pattern – Mild type II pneumocyte hyperplasia – Mild interstitial fibrosis (which is mainly peri-bronchiolar)
- 12. DIFFERENTIAL DIAGNOSIS • Langerhans cell histiocytosis – Frequent cystic changes (imaging – gross) – Mainly interstitial process (not intraluminal) – Aggregates of Langerhans histiocytes • Convoluted / folded / grooved / kidney-shaped nuclei • Positive CD1a – Increased eosinophils – can show focal DIP-like areas • Hypersensitivity pneumonitis – History of exposure to Antigens – Mainly bronchiolo-centric – Poorly formed granulomas and/or giant cells – Intra-luminal BOOP-like plugs & interstitial fibroblastic foci – can show focal DIP-like areas
- 13. DIFFERENTIAL DIAGNOSIS • Other interstitial pneumonias and processes – Acute interstitial diseases: Hyaline membrane or fibrin – Cryptogenic organizing pneumonia: Bronchiolocentric - Intraluminal organization rather macrophages – Nonspecific interstitial pneumonia: Uniform, Diffuse interstitial inflammation/fibrosis – few intra-alveolar macrophages – Lymphocytic interstitial pneumonia: diffuse alveolar septa expansion by chronic inflammatory cells - few intra-alveolar macrophages
- 14. DIFFERENTIAL DIAGNOSIS Clinical Diagnosis Histologic Pattern Duration of Illness Radiological findings HRCT Prognosis Interstitial pulmonary fibrosis Usual interstitial pneumonia Chronic > 12 months • Subpleural & bibasal predominance • Honeycombing • Reticular opacities • Ground-glass opacities • Traction bronchiectasis 5-year survival: 20% Nonspecific interstitial pneumonia Nonspecific interstitial pneumonia Subacute – chronic Months - years • Bilateral, symmetrical & basal • Ground-glass opacities • Reticular opacities • Lower lobe volume loss • Rare honeycombing • Cellular NSIP 10-year survival: more than 90% • Fibrotic NSIP 5-year survival: 90% 10-year survival: 35% Cryptogenic organizing pneumonia Organizing pneumonia Subacute < 3 months Subpleural, peribronchial patchy consolidation / nodularity 5-year survival >95%
- 15. DIFFERENTIAL DIAGNOSIS Clinical Diagnosis Histologic Pattern Duration of Illness Radiological findings HRCT Prognosis Acute respiratory distress syndrome Diffuse alveolar damage Acute 1 – 2 weeks • Diffuse pulmonary infiltrate • Ground-glass opacities 40%-60% mortality rate in < 6 months Desquamative interstitial pneumonia Desquamative interstitial pneumonia Subacute Weeks - months • Subpleural predominance • Ground-glass opacities • Reticular opacities • Thin-walled cysts • Rare honeycombing 5-year survival: more than 95% Respiratory bronchiolitis– associated interstitial lung disease Respiratory bronchiolitis Subacute Weeks - months • Diffuse bronchial wall thickening • Centrilobular nodules • Patchy ground-glass opacity No deaths reported
- 16. DIFFERENTIAL DIAGNOSIS • Increased intra-luminal foamy macrophages – Following bronchiolar obstruction (localized process) – Macrophages are not pigmented (unless smoker) – No associated interstitial pneumonitis or fibrosis • Pneumoconiosis (especially Asbestosis) and drug reactions should be ruled out as it may show DIP-like areas – History is important – In case of Asbestosis asbestos bodies should be seen
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