What is the best approach to manage cough in a patient with acute hypersensitivity pneumonitis, a history of environmental antigen exposure, and presenting symptoms of cough and wheezing?

Managing Cough in Acute Hypersensitivity Pneumonitis

The most critical intervention is immediate and complete removal of the offending environmental antigen exposure, combined with systemic corticosteroids for patients with physiologic impairment. 1

Immediate Diagnostic Workup

Blood Tests to Order

• Complete blood count with differential - look for elevated acute phase reactants and inflammatory markers 2
• Serum precipitating antibodies against suspected environmental antigens (avian proteins, mold antigens, etc.) - these confirm antigen exposure and are a diagnostic hallmark, though their presence alone doesn't confirm HP 1, 3, 2
• Basic metabolic panel - to assess baseline organ function before corticosteroid therapy 2

Imaging Studies Required

• High-resolution chest CT (HRCT) - this is essential and should show bilateral ground-glass opacities with mosaic pattern in middle and lower lung zones, ill-defined centrilobular nodules, and air-trapping on expiration 3, 2
• Chest radiograph - typically reveals widespread ground-glass attenuation and nodular or reticulonodular shadowing, though HRCT is superior 2, 4

Additional Diagnostic Tests

• Pulmonary function tests - expect restrictive ventilatory defect with reduced lung volumes and hypoxemia at rest that worsens with exercise 2
• Bronchioloalveolar lavage (BAL) - look for increased total cell count with >50% T lymphocytes, >3% neutrophils, and >1% mast cells 1, 3
• Transbronchial lung biopsy (if diagnosis uncertain) - shows bronchiolocentric granulomatous inflammation, lymphocytic alveolitis, and ill-defined non-necrotizing granulomas 1, 3

Treatment Algorithm

Step 1: Antigen Elimination (Mandatory)

Complete removal of the causative exposure is the cornerstone of therapy and must be implemented immediately. 1

• Identify the specific antigen through detailed environmental history (birds, mold, occupational exposures) 1, 3
• Remove patient from exposure source or eliminate antigen from environment 1, 3
• Document temporal relationship between exposure cessation and symptom improvement 1

Step 2: Systemic Corticosteroids

Initiate systemic corticosteroids in patients with evidence of physiologic impairment (abnormal pulmonary function tests, hypoxemia, or significant symptoms). 1

• Prednisone 0.5-1.0 mg/kg/day initially, followed by gradual tapering over 2 months 3, 2
• Corticosteroids improve pulmonary function and symptoms in acute disease, though long-term efficacy on outcomes remains unproven 1
• Monitor for symptomatic improvement within weeks to months 1

Step 3: Exclude Common Cough Causes

Before attributing cough solely to HP, systematically exclude other common etiologies that may coexist: 1

• Upper airway cough syndrome (UACS) - treat with first-generation antihistamine/decongestant if present 1
• Asthma or bronchial hyperresponsiveness - given the wheezing, perform spirometry and consider bronchoprovocation challenge; treat with inhaled bronchodilators and corticosteroids if confirmed 1
• GERD - evaluate and treat if symptoms suggest this diagnosis 1

Monitoring Response to Treatment

Expected Clinical Improvements

• Symptom resolution - 41-53% of patients experience sustained decrease in dyspnea and cough after antigen avoidance 1
• Pulmonary function improvement - expect improvement or normalization of FVC within 3-4 months of antigen cessation 1
• Radiologic improvement - repeat HRCT at 3-6 months to document resolution of ground-glass opacities 1

Prognostic Indicators

• Clinical improvement with antigen avoidance is associated with decreased mortality (HR 0.14-0.18) 1
• Continued exposure leads to progressive disease and potential respiratory failure 1

Critical Pitfalls to Avoid

• Do not delay antigen removal - this is more important than corticosteroid therapy and directly impacts mortality 1
• Do not assume cough is solely from HP - the pathophysiology involves bronchiolitis with potential airflow limitation similar to asthma, so treat the wheezing component appropriately 1
• Do not use inhaled corticosteroids alone - while theoretically useful, there is insufficient data to support this approach as primary therapy in acute HP 1
• Do not continue corticosteroids indefinitely - taper after 2 months as prolonged use has significant side effects without proven long-term benefit 1