Treatment and Management of Hypersensitivity Pneumonitis to Improve Survival
Complete antigen avoidance is the cornerstone of hypersensitivity pneumonitis (HP) management and should be implemented immediately to prevent disease progression and improve survival. 1
Classification and Prognostic Factors
- HP should be classified based on the presence or absence of fibrosis, as fibrotic HP has significantly worse prognosis than non-fibrotic HP 1
- The likelihood of identifying an inciting antigen (IA) should be determined, as this has important implications for management and survival 1
- Negative prognostic factors in fibrotic HP include less than 50% lymphocytes in bronchoalveolar lavage (BAL) and the presence of honeycombing on imaging 2
Antigen Avoidance Strategy
- A thorough environmental and occupational exposure history is essential to identify potential inciting antigens 1
- For occupational exposures, consider involving an occupational medicine specialist and environmental hygienist during the diagnostic workup 1
- Complete antigen avoidance results in no recurrence or development of fibrosis in non-fibrotic HP patients 2
- For hot-tub lung or other mycobacterial-related HP, complete avoidance of the antigen source is paramount - indoor hot tubs should be moved outdoors or completely removed 1
Pharmacological Management
Non-fibrotic HP
- For patients with severe disease or respiratory failure, prednisone at 1-2 mg/kg/day tapered over 4-8 weeks is recommended 1
- Corticosteroids may hasten recovery and improve gas exchange but should be used in conjunction with antigen avoidance 1
- In cases of mycobacterial HP (hot-tub lung), antimycobacterial therapy may be given for 3-6 months if symptoms persist after antigen avoidance 1
Fibrotic HP
- In patients with fibrotic HP, especially those with progressive disease, immunosuppressive therapy may be needed when complete antigen avoidance cannot be achieved 1
- Clinical improvement after antigen avoidance in fibrotic HP is associated with decreased mortality (HR, 0.18; 95% CI, 0.04-0.77) 1
- Nintedanib has been approved for slowing the progression of chronic fibrosing ILDs with a progressive phenotype, including progressive fibrotic HP 3
Monitoring and Follow-up
- Regular assessment of lung function (FVC%, DLCO%) is essential to monitor response to treatment 1
- In non-fibrotic HP, improvement in lung function parameters typically occurs within 3-4 months after antigen avoidance 1
- Continued surveillance for exposure and patient education focused on antigen avoidance should be performed at every visit 1
Special Considerations
- In cases where the inciting antigen cannot be identified (which is common in fibrotic HP), more aggressive immunosuppression may be necessary 1
- Non-pharmacological interventions such as oxygen therapy, pulmonary rehabilitation, and supportive care are important components of overall management for progressive HP 3
- For immunocompromised patients or those with persistent disease despite antigen avoidance and corticosteroids, antimicrobial therapy may be considered 1
Pitfalls and Caveats
- Failure to improve with antigen avoidance does not rule out HP, especially in fibrotic disease 1
- Relying solely on clinical improvement with medical therapy to confirm or rule out HP diagnosis is not recommended 1
- Incomplete antigen avoidance in non-fibrotic HP leads to recurrence and/or development of fibrosis in over 50% of patients 2
- In fibrotic HP, incomplete antigen avoidance tends to be associated with poorer survival (HR 3.452,95% CI 0.964-12.359) 2