What is the treatment for hypersensitivity pneumonitis?

Treatment of Hypersensitivity Pneumonitis

The cornerstone of hypersensitivity pneumonitis (HP) treatment is identification and complete avoidance of the inciting antigen, which is essential for all patients and may lead to complete resolution in early detected non-fibrotic HP. 1

Antigen Identification and Avoidance

• A thorough clinical history of exposures is critical to establish the type, extent, and temporal relationship of exposure(s) to symptoms 2
• Classification of patients based on likelihood of occupational or environmental inciting antigen exposure is recommended 2
• Consider including an occupational medicine specialist and environmental hygienist during diagnostic workup when the source is obscure 2
• Clinical improvement after antigen avoidance is associated with decreased mortality (HR, 0.18; 95% CI, 0.04-0.77) 1
• When remediation is not possible, removal of the patient from the suspected environment is necessary 1

Treatment Algorithm Based on Disease Classification

1. Non-Fibrotic HP

• First-line: Complete antigen avoidance - may lead to complete resolution 1
• For severe disease or respiratory failure:
  • Corticosteroids: Prednisone 1-2 mg/kg/day tapered over 4-8 weeks 1
  • Continue only if objective improvement is documented 1
  • Therapy duration based on clinical response 1

2. Fibrotic HP

• First-line: Complete antigen avoidance - though less likely to result in complete resolution 2
• For progressive fibrotic disease:
  • Nintedanib (tyrosine kinase inhibitor) - approved for slowing progression of chronic fibrosing ILDs with progressive phenotype 1, 3
  • Longer-term management with regular monitoring of pulmonary function tests and imaging 1
  • Consider lung transplantation for end-stage disease 1

3. Special Situations

• For hot-tub lung: Avoid indoor hot-tub use 1
• For metal grinders: Avoid metalworking fluid exposure 1
• For MAC hypersensitivity-like disease with persistent symptoms: Consider antimycobacterial therapy for 3-6 months 1

Monitoring and Follow-up

• Regular assessment of clinical improvement, pulmonary function, and radiographic changes 1
• Note that absence of clinical improvement with antigen avoidance does not exclude HP diagnosis 2
• Patients requiring immunosuppressive therapy generally have worse baseline lung function and increased mortality 1

Important Considerations and Pitfalls

• Key pitfall: Failure to identify and remove the inciting antigen 1
• In 30-60% of cases, an exposure cannot be identified despite thorough investigation 1, 4
• Serum antigen-specific IgG/IgA testing alone should not be relied upon to confirm or rule out HP diagnosis 2
• Clinical improvement with medical therapy alone should not be used to confirm HP diagnosis 2
• The presence of fibrosis significantly impacts prognosis and treatment approach 1
• Telomere-related gene mutations are associated with shortened survival in HP 1

Supportive Care

• Oxygen therapy for hypoxemic patients 1, 3
• Pulmonary rehabilitation 1, 3
• Regular monitoring for disease progression, especially in fibrotic HP 1

By following this treatment algorithm with emphasis on antigen identification and avoidance as the primary intervention, outcomes for patients with hypersensitivity pneumonitis can be optimized, particularly when intervention occurs before the development of fibrosis.