What is the treatment for chronic hypersensitivity pneumonitis (HP)?

Treatment for Chronic Hypersensitivity Pneumonitis

The cornerstone of treatment for chronic hypersensitivity pneumonitis (HP) is complete antigen avoidance, which should be implemented wherever possible, supplemented with immunosuppressive therapy for patients with fibrotic disease or those who continue to progress despite antigen avoidance. 1

Classification and Prognostic Factors

• HP should be classified based on the presence or absence of fibrosis rather than using time-based classifications (acute, subacute, chronic), as fibrotic HP has significantly worse prognosis 2
• The likelihood of identifying an inciting antigen (IA) should be determined, as unidentified IA is associated with shortened survival (HR 1.76; 95% CI 1.01-3.07) 2
• Patients with fibrotic HP may develop a progressive phenotype characterized by worsening fibrosis, decline in lung function, and early mortality 3

Antigen Avoidance

• Complete antigen avoidance is the mainstay of treatment for all forms of HP 4
• In non-fibrotic HP, complete antigen avoidance can result in no recurrence or development of fibrosis 5
• Clinical improvement with antigen avoidance supports the diagnosis of HP but lack of improvement does not rule it out, especially in fibrotic disease 2
• For occupational exposures, consider involving an occupational medicine specialist and environmental hygienist 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, 6
• Corticosteroids may hasten recovery but should be used in conjunction with antigen avoidance 6
• Clinical improvement with medical therapy supports but does not confirm the diagnosis of HP 2

Fibrotic HP

• Immunosuppressive therapy is indicated for patients with fibrotic HP, especially those with progressive disease 1, 3
• Options include:
  • Corticosteroids (prednisone) as first-line therapy 2
  • Steroid-sparing agents such as mycophenolate mofetil or azathioprine, which can significantly alter the slope of monthly FVC decline (0.7% vs 0.2%; p=0.001) 2
  • Nintedanib, a tyrosine kinase inhibitor, has been approved by the FDA 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
• For fibrotic HP, monitor for disease progression despite treatment 3

Pitfalls and Caveats

• Failure to respond to medical treatment does not necessarily exclude the diagnosis of HP as response rates can be highly variable 2
• Clinical improvement with medical therapy is much more common in non-fibrotic HP than in fibrotic HP 2
• Measurable clinical improvement may not occur if:
  • The remediated antigen is not causative
  • There are multiple exposures causing disease
  • Complete avoidance cannot be achieved
  • The patient has severe or progressive pulmonary fibrosis 2
• In a significant proportion of patients with fibrotic HP, an antigen will not be identified, which may necessitate more aggressive immunosuppression 1, 7

Non-pharmacological Interventions

• Oxygen therapy, pulmonary rehabilitation, and supportive care may be important components of the overall care of patients with progressive HP 3
• Patient education focused on antigen avoidance should be performed at every visit 1