Medicine Marrow Pg 251-260 (Pulmonology)

X-Ray Findings against Diagnosis of ABPA

• Bronchial wall thickening and small nodules are unlikely to indicate ABPA.
• Pleural involvement, lymphadenopathy, consolidation, air fluid levels, and perihilar involvement are against a diagnosis of ABPA.

Treatment of ABPA

• Steroids are the first-line treatment for ABPA, administered for 12 weeks.
• Itraconazole is a second-line therapy used in steroid-dependent or relapsing cases, or when there's no resolution with steroids.
• Omalizumab is another treatment option.
• IgE levels should be monitored periodically.

Hypersensitivity Pneumonitis (HP)

• HP, also known as extrinsic allergic alveolitis, is a lung disease typically affecting non-smokers.
• Repeated inhalation of organic dust triggers a hypersensitivity reaction, primarily type IV, but also type III.
• Inflammation affects the terminal airways, alveoli, and interstitium, predominantly involving lymphocytes.

Pathology of HP

• HP does not involve type I hypersensitivity.
• Initially, diffuse pulmonary infiltrates are observed.
• Non-caseating granulomas, eosinophilia, elevated IgE levels, migratory lung infiltrates, and a reticulo-nodular pattern are characteristic features.

Etiology of HP

• Farmer's lung is the most common type, caused by moldy hay containing Thermoactinomyces vulgaris.
• Bagassosis is the second most common type, caused by moldy sugarcane.
• Other HP types include:
  • Mushroom worker's lung, caused by moldy compost/mushroom (e.g., Aspergillus clavatus).
  • Compost lung, caused by compost containing Cladosporium or MAC (Mycobacterium avium complex).
  • Tobacco worker's lung, caused by mold on tobacco.
  • Malt worker's lung, caused by barley.
  • Cheese washer's lung.
  • Hot tub lung/Humidifier lung/Air conditioner lung, caused by avian droppings.
  • Bird fancier's lung, caused by pigeons, parrots, or chickens (e.g., Rhizopus).
  • Wood trimmer's lung, caused by wood pulp.
  • Familial HP, caused by polyurethane foams (e.g., Isocyanate) and Bacillus subtilis.
  • Chemical worker's lung.

Acute Eosinophilic Pneumonia (AEP)

• Peripheral blood: Leukocytosis.
• Bronchoalveolar lavage (BAL): Increased eosinophils.
• IgE: Increased.
• X-ray: Bilateral infiltrates, resembling a negative of pulmonary edema.
• CT: Diffuse parenchymal ground-glass opacity and consolidation.

Chronic Eosinophilic Pneumonia (CEP)

• BAL: Eosinophils greater than 240% of normal values.
• Imaging: Reverse bat-wing appearance or photographic negative of pulmonary edema.
• Perihilar sparing: Present.
• Peripheral opacities: Present.
• CT: Peripheral pulmonary opacities, predominantly on the right side.

Idiopathic Hypereosinophilic Syndrome

• Peripheral eosinophilia: Greater than 1500 cells per microliter for more than six months.
• X-ray: Transient focal or diffuse pulmonary infiltrates.
• CT: Peripheral pulmonary opacities, predominantly on the right side.

Treatment of Eosinophilic Lung Diseases

• AEP and CEP: Steroids.
• Idiopathic hypereosinophilic syndrome: Steroids, but often unresponsive.

Presentation of Hypersensitivity Pneumonitis

• Acute: Self-resolving.
• Chronic: Can cause fibrosis leading to interstitial lung disease (ILD).

Clinical Features of HP

• Acute form: Fever, chills, cough with an elevated erythrocyte sedimentation rate (ESR). The symptoms resolve within 2-4 days.
• Subacute form: Gradual, progressive dyspnea and cough with fatigue. Systemic symptoms are absent. Upper lobe involvement is common.

Complications of HP

• Bird fancier's lung: Rarely causes fibrosis or ILD.
• Farmer's lung: May cause emphysematous changes.

Causes of Non-caseating Granulomas

• HP, tuberculosis (30%), lymphoma, sarcoidosis, cat scratch disease, Crohn's disease, and berylliosis.

Diseases Causing Emphysematous Changes

• Farmer's lung, cryptogenic organizing pneumonia and (rarely) coal worker's pneumoconiosis.

Management of HP

• Investigations:
  • Serum precipitins: May be positive but are non-specific due to Type III hypersensitivity.
  • BAL: Shows lymphocytosis with CD8 cells exceeding CD4 cells.

Allergic Bronchopulmonary Aspergillosis (ABPA)

• Causative organism: Aspergillus fumigatus is the most common causative agent, followed by Aspergillus niger, Aspergillus flavus, and Aspergillus terreus.

Identifying Features of Aspergillus

• Conidiophore, septate hyphae, and saprophytic nature are key identifying features.

Lung Manifestations of Aspergillus

Pathogenesis of ABPA

• ABPA develops in patients with chronic asthma or cystic fibrosis.
• Organism colonizes the airway, leading to a complex hypersensitivity reaction involving both type I and type III hypersensitivity.
• Eosinophilia and elevated IgE levels are observed. This leads to eosinophilic inflammation and mucus plugs containing septate hyphae within the bronchial wall.
• Migratory lung infiltrates are a common finding. Inflammation weakens the bronchial wall, resulting in bronchiectasis, cough with sputum, atelectasis, and bronchial mucosal plugs in sputum containing hyphae and eosinophils.

Symptoms of ABPA

• Acute on chronic disease:
  • Chronic component: Malaise, anorexia, weight loss, hepatosplenomegaly, and lymphadenopathy.
  • Acute component: Paroxysmal dry cough, dyspnea or wheezing, particularly at night, resembling status asthmaticus.

Investigations for ABPA

• Laboratory findings:

  • Significant peripheral eosinophilia (greater than 3000 cells per cubic millimeter).
  • BAL: Intense eosinophilic alveolitis (greater than 40%).
  • IgE: Greater than 1000 IU/mL.

• Radiological findings:

  • Bilateral, indefinite mottling, uniformly throughout both lung fields, primarily in the middle and lower lobes.
  • Increased bronchovascular markings.
  • Cavitation and pleural effusion.

Treatment of ABPA

• The first-line treatment for ABPA is diethylcarbamazine (DEC), a medication effective against both adult filariаe and microfilariаe.
• DEC is administered orally at a dose of 2 mg/kg three times a day (TID) for 14 to 21 days or up to four weeks.
• Clinical improvement is typically seen within 7 days, and acute relapses occur in up to 20% of cases, requiring higher doses of DEC.

Unknown Causes of Eosinophilic Lung Disease (ELD)

Notes on Unknown Causes of Eosinophilic Lung Disease

• Respiratory system (RS) involvement: TB-like presentation, acute respiratory distress syndrome (ARDS), pulmonary hypertension (pulm HTN).
• Central nervous system (CNS): Neuropsychiatric dysfunction (60%).
• Cardiovascular system (CVS): Eosinophilic myocarditis, endomyocardial fibrosis.

Evaluation of ABPA

• Criteria for Diagnosis:

  • 1. Predisposing asthma or cystic fibrosis (CF).
  • 2. Obligatory Criteria:
    • IgE > 1000 IU/mL.
    • Positive immediate skin test or increased IgE antibody to Aspergillus.
  • 3. Supportive Criteria (at least 2):
    • Eosinophilia > 500/μL.
    • Presence of precipitins or elevated IgG antibody to Aspergillus.
    • Consistent radiographic opacities.

• Most useful test: IgE levels.

Pulmonary Function Testing (PFT) Pattern in ABPA

• Obstructive pattern, predominantly due to bronchiectasis.
• Stage 5 ABPA: Fibrosis, resulting in a restrictive pattern.

Imaging Findings in ABPA

• Fleeting infiltrates: Irregular, transient parenchymal infiltrates.
• Finger in glove: Mucoid impaction in dilated bronchi.
• Tramtrack shadows: Parallel linear shadows extending from the hilum into the bronchial distribution.
• Trees in bud: Cylindrical and proximal bronchiectasis of the upper lobe with thickening of the bronchial walls (nodules).
• Saccular dilatation: Visible saccular dilatation.

Lung Conditions

• ABPA (Allergic Bronchopulmonary Aspergillosis).
• Langerhans cell histiocytosis.
• Hypersensitivity pneumonitis.
• Tuberculosis (TB).

Features of Bronchiectasis in ABPA

• Bilateral involvement.
• Upper lobe involvement.
• Central location in the upper lobes.
• Proximal location in the upper lobes.
• Tree in bud appearance.
• Cystic bronchiectasis in central aspects.

CT (Lung Window) in ABPA

• Soft tissue upper lobe nodules represent mucoid impaction within dilated bronchi.

Clinical Features of ABPA

• Presentation: Recurrent acute exacerbations in patients with chronic, steroid-dependent, or treatment-refractory asthma or cystic fibrosis.
• Symptoms: Fever, cough with expectoration (brownish, thick mucosal plug).
• Signs: Present in only 15-20% of cases.
  • Crackles.
  • Clubbing.

Course of ABPA

• Rarely causes upper lobe fibrosis.

Causes of Upper Lobe Fibrosis

• Rheumatology:
  • Ankylosing spondylitis.
  • Sarcoidosis.

HRCT Thorax in ABPA

• Central bronchiectasis.

CT Chest in ABPA

• Hyperattenuated mucus.

Pleural Anatomy

• Pleural Cavity: Lined by mesothelial cells that produce surfactant.
• Normal amount of pleural fluid (PF): 10-20 mL.
• Negative intrapleural pressure: Maintained by pleural lymphatics and a vacuum.
• Coupling Organ: Connects the lungs and chest wall.
• Types of Pleura:
  • Parietal: Develops from somatopleuric mesoderm (pain-sensitive).
  • Visceral: Develops from splanchopleural mesoderm (pain-insensitive).
• Minimum amount of Pleural Fluid for Detection:
  • Ultrasound and Lateral X-ray: 50 mL.
  • CXR Posterior-anterior (PA) View: 200 mL.
  • Clinically detectable: 300 mL.

Composition of Pleural Fluid

• Macrophages: 70%.
• Lymphocytes: 25%.
• Mesothelial cells: 1-5%.

Pleural Fluid Chemistry

• Glucose: Similar to blood glucose.
• Protein: 1-1.5 g/dL.
• Lactate dehydrogenase (LDH): Less than 50% of plasma LDH.

Light's Criteria (Exudative versus Transudative Pleural Effusions)

• If any one criterion is met, the effusion is classified as exudative.
• If all three criteria are negative, the effusion is classified as transudative.

Disadvantages of Light's Criteria

• In patients with congestive heart failure (CCF) receiving diuretics, one-third of cases are misclassified as exudative.
• Instead, consider using the serum pleural fluid albumin gradient (higher gradient indicates a transudative effusion).

Occupational Exposures

• Silicosis, coal worker's pneumoconiosis, and beryliosis.

PET Imaging in HP

• Chronic form (ILD/fibrosis): Diffuse opacities.

CXR in HP

• Diffuse opacities.
• Reticulonodular shadows.

CT Imaging in HP

• Centrilobular nodules.
• Bilateral ground glass opacities (GGO).
• Mosaic attenuation or "head cheese" pattern (varying densities on the same CT).

BAL Lymphocytosis in HP

• CD4 cells greater than 2: Suggestive of sarcoidosis.
• CD8 cells: Dominant in hypersensitivity pneumonitis.

Treatment of HP

• Subacute form: Responds to steroids.
• Fibrosis: Irreversible.

Differences Between HP and ABPA

Note on Image Descriptions

• The document contains radiographic images of the chest, likely CXR and CT scans.
• These images demonstrate various patterns of lung opacities and/or nodules, suggesting potential lung conditions like hypersensitivity pneumonitis and allergic bronchopulmonary aspergillosis.
• Written descriptions of the images and associated conditions are provided.
• A table summarizes key differences between hypersensitivity pneumonitis and allergic bronchopulmonary aspergillosis.

Test your knowledge on Allergic Bronchopulmonary Aspergillosis (ABPA) and hypersensitivity pneumonitis. This quiz covers diagnostic findings, treatment regimens, and associated pathologies. Enhance your understanding of these respiratory conditions and their management.