What is the treatment for hypersensitivity pneumonitis?

Treatment of Hypersensitivity Pneumonitis

The cornerstone of hypersensitivity pneumonitis (HP) treatment is complete avoidance of the inciting antigen, which should be implemented as the first and most crucial therapeutic step for all patients. 1 Additional therapies depend on disease phenotype (non-fibrotic vs. fibrotic) and severity.

Antigen Avoidance

• Identification and removal of the inciting antigen is paramount 2, 1
• For patients with documented HP, complete avoidance of exposure to the identified antigen is essential 2
• For hot-tub lung, avoid indoor hot-tub use; for metal grinders, avoid metalworking fluid exposure 2
• Clinical improvement after antigen avoidance is associated with decreased mortality (HR, 0.18; 95% CI, 0.04-0.77) 2
• Failure to identify and remove the inciting antigen is a key pitfall in management 1

Treatment Algorithm Based on Disease Phenotype

Non-Fibrotic HP

1. First-line: Antigen avoidance

   • May lead to complete resolution in early detected non-fibrotic HP 2
   • When remediation is not possible, remove patient from suspected environment 2

2. Second-line: Corticosteroids

   • Indicated for severe acute/subacute inflammation 1, 3
   • Typically prednisone at 1-2 mg/kg/day tapered over 4-8 weeks for patients with severe disease or respiratory failure 2
   • May hasten recovery and improve gas exchange 2

3. Monitoring

   • Regular follow-up to assess clinical improvement, pulmonary function, and radiographic changes 3

Fibrotic HP

1. First-line: Antigen avoidance

   • Note: Many fibrotic HP patients fail to improve with antigen avoidance alone 2

2. Second-line: Immunosuppressive therapy

   • Consider for progressive disease despite antigen avoidance 3, 4
   • Options include:
     • Corticosteroids (prednisone)
     • Steroid-sparing agents: azathioprine or mycophenolate mofetil
     • Treatment-emergent adverse events are 54% less frequent with azathioprine and 66% less frequent with mycophenolate mofetil compared to prednisone alone 4

3. Third-line: Antifibrotic therapy

   • Nintedanib (tyrosine kinase inhibitor) for progressive fibrotic HP 1, 5
   • FDA-approved for slowing progression of chronic fibrosing ILDs with progressive phenotype 5

4. Advanced disease management

   • Oxygen therapy for hypoxemia 1, 5
   • Pulmonary rehabilitation 1, 5
   • Lung transplantation for end-stage disease 1

Special Considerations

Hot-Tub Lung (MAC-Related HP)

• Complete avoidance of indoor hot tubs 2
• Corticosteroids may be beneficial 2
• Antimycobacterial therapy may be given for 3-6 months if symptoms persist 2
• Not all MAC hypersensitivity-like disease needs antimycobacterial therapy 2

Duration of Therapy

• For non-fibrotic HP: Therapy duration based on clinical response
• For fibrotic HP: Longer-term management often required with regular monitoring of pulmonary function tests and imaging 1

Important Caveats

• Up to 30-60% of cases have no identifiable exposure despite thorough investigation 1
• Presence of fibrosis significantly impacts prognosis and treatment approach 1
• Long-term corticosteroid therapy should only be continued if objective improvement is documented 3
• Patients who require immunosuppressive therapy generally have worse baseline lung function and increased mortality compared to those who don't 4
• The absence of clinical improvement with antigen avoidance does not exclude the diagnosis of HP 2

Monitoring Response

• Regular pulmonary function tests (PFTs)
• Serial imaging to assess for progression or improvement
• Clinical assessment of symptoms
• Consider repeating bronchoscopy with BAL in select cases to assess for persistent lymphocytosis

By following this structured approach to HP management with emphasis on antigen avoidance as the primary intervention, outcomes related to morbidity, mortality, and quality of life can be optimized.